When United Airlines Flight 718 and Trans World Airlines Flight 2 collided in midair above the Grand Canyon on a June morning in 1956—the spinning props of the United DC-7 slicing into the fuselage of the TWA L-1049 Super Constellation as its wing cut the aircraft in two—not a single known person on the ground saw it. Not a soul witnessed what we can only imagine were violent fireballs and streaming plumes of black smoke. No one even knew that the canyon’s mighty peace had been disturbed—save, of course, the 128 people on board both aircraft, who lived through mere seconds of terror no human should ever know, the last seconds of their lives.

This despite the fact that the Grand Canyon was and is one of the world’s most popular tourist attractions, even in the mid-1950s drawing around a million visitors a year. Despite the fact that the planes collided around 10:30 a.m. on a clear summer weekend day. And despite the fact that almost every railed ledge in the tourist area afforded unobstructed views, so the folks visiting from Waukegan and Sacramento and Hartford, their new Kodak Brownie cameras hanging from their necks, could see for miles across the massive chasm.

Despite all that, two planes collided spectacularly and nobody saw; in the quiet after the crash, it was as if it had never happened. That’s how vast the Grand Canyon truly is. The greatest disaster in aviation history, up to that point, still gets lost in the scale of the terrain.

In fact, nobody anywhere knew anything was wrong until about an hour later, when both flights failed to check in at their shared radio waypoint, known as Painted Desert. There were no radar blips that suddenly disappeared from an air traffic controller’s screen, no frantic bystanders rushing to the scene, no chilling mayday calls that spurred rescue teams into action. Though one such call was sent—a calm, defeated declaration that “Salt Lake, United 718 . . . ah . . . we’re going in” from United copilot Robert Harms, transmitted to the Salt Lake City control center—it was garbled and not properly identified until weeks later, during the investigation.

Arrows show the approximate locations where the TWA and United planes crashed into the North Rim of the Grand Canyon. The collision killed 128 passengers and crew, making it the worst air disaster in commercial aviation at the time.

The only sign of trouble was a lingering wisp of smoke that a private pilot noticed while flying over the canyon. On that day its walls would have been bathed in pure southwestern sunlight speckled with scrolling cloud shadows—a good day to fly. Presuming it to be a brush fire, the pilot later returned to investigate after hearing news reports of the missing aircraft; he was the first to spot the wreckage.

People would learn of the collision, of course. Within hours, the world would learn of it. The dramatic backdrop—the majestic Grand Canyon, steep rock walls looming above the rivers, revealing entire eras of geological formation in their colored striations—heightened the sense of tragedy when it was reported on the evening news, giving pause to a growing populace eager for the convenience and the excitement of flying around the country. People were mystified. How could two airplanes flying through the wide-open skies of the American West intersect at the same tiny point in the vastness of three-dimensional space? What were the odds?

It’s easy now for us to look back at a 70-year-old calamity and think, That was early days. The industry was moving too fast, the technology was too advanced for its own good.

That would never happen today.

Then: January 2025. The midair collision of American Airlines Flight 5342 and a U.S. Army Black Hawk helicopter over the Potomac River in Washington, D.C., killed 67 people. It happened barely three miles from the White House.

Are we so smart? Have we figured it out? And are there clues from 1956 that hold insight into how to prevent it from happening again, and again, and again?

Air travel in the 1950s was at once regal and primitive. Piston-powered airliners crisscrossed largely empty skies at what today would seem a leisurely pace. Transcontinental flights would often make multiple stops, in rustic Old West outposts like Oklahoma City and bustling heartland metropolises like Chicago. Journeys from New York to Los Angeles could take 10 or more hours, with the gleaming aluminum luxury liners soldiering languorously through the air at 300 mph, nothing like the withering 600mph paces the Jet Age would bring once it took hold in the early 1960s.

Yet the mere notion of reaching the opposite coast within a single day was beyond romantic, and the air travel experience often glamorous. Most airlines, in fact, operated dedicated first-class-only flights on popular routes. These flights had excellent cuisine, cocktail lounges, curtains on the windows, and roomy seats. Passengers could smoke in the main cabin or light up cigars and pipes in the lounge. The thunderous roar of four 3,400-horsepower, 18-cylinder radial engines furiously spinning their 14-foot-diameter Hamilton Standard Hydromatic props still wasn’t as brain-meltingly loud as the narrow, screeching jet engines travelers would be subjected to once the Boeing 707 and Douglas DC-8 debuted in 1958 and 1959, respectively. Air travel in the ’50s was a new, exhilarating alternate reality.

The United and TWA flights that left Los Angeles International Airport on June 30, 1956, were among those special first-class-only flights. After boarding mere feet from each other at adjacent gates, the two aircraft taxied to the runway. TWA 2 took off first, at 9:01 a.m. local time, on its way to Kansas City Downtown Airport with 70 on board. At the controls: Captain Jack Gandy, First Officer James Ritner, and Flight Engineer Forrest Breyfogle. United 718 rolled down the same runway at 9:04 a.m., headed for Chicago’s Midway Airport with 58 on board, including Captain Robert Shirley, First Officer Robert Harms, and Flight Engineer Gerard Fiore. Both aircraft had two flight attendants on duty. Neither had flight data recorders or cockpit voice recorders, which were not in widespread use at the time. The airplanes were supposed to take off about 15 minutes apart, but both had minor delays that separated their departures by just three minutes.

The airplanes were cleared to travel routes set by their airlines—TWA 2 past Daggett, California, at an altitude of 19,000 feet, and United 718 through Palm Springs, California, at 21,000 feet. Both were operating under visual flight rules (VFR), meaning the crews were obligated to scan for weather challenges and other aircraft visually. Their paths, diverging initially, would converge again after the first waypoints and then cross over each other near the Grand Canyon, just before the Painted Desert region. However, their staggered timing, different speeds (TWA 2 at 270 knots, United 718 at 288 knots), and 2,000-foot vertical separation should have kept them out of each other’s way.

Both flight crews, however, opted to fly “off-airways” after getting their initial clearances, meaning they would take more direct paths to their next waypoints than they would have by staying on prescribed airline routes, which are meant to accommodate a wider range of flights. They’d also be in uncontrolled airspace, with no electronic tracking by any air traffic controllers (ATC), and were required to stay in visible airspace so as to avoid other aircraft.

TWA 2 checked in with a company dispatcher at 9:21 a.m., requesting an increase to 21,000 feet to avoid turbulence. (Airline dispatchers often relayed communications for their pilots if the aircraft were out of radio range of controllers farther down the route.) Controllers at Los Angeles Center further checked with the Salt Lake City control center where TWA 2 was headed, and that controller, in Salt Lake, flagged the altitude as being assigned to United 718. He declined the request. A subsequent request for “1,000 on top”—meaning the plane would stay 1,000 feet above the cloud tops—was approved, but TWA 2 still had the responsibility of maintaining visual separation from other aircraft, and it was told of United 718’s altitude. TWA 2 then settled in at 21,000 feet, matching United’s altitude.

At 10:13, both airlines had reported the flights’ revised positions and route estimates to the Salt Lake City controller, with both expected to arrive at the Painted Desert line at 10:31 while at 21,000 feet. The Salt Lake City controller wasn’t required to pass potential conflicts on to the aircraft, as the planes were in uncontrolled airspace and flying VFR; the pilots were responsible for seeing each other and avoiding other aircraft, any number of which could be in the area without the knowledge of ATC. Investigations indicated that sharing this information could have prevented the accident, but didn’t implicate the controller because he was managing a multitude of flights in the area and was correct to assume the flights would “see and avoid” each other, per ATC procedures.

With no active radar tracking above the Grand Canyon, the flight crews were effectively on their own.

Though the airplanes were both due to arrive at the Painted Desert line at the same time, 10:31 a.m., both were tracking a few minutes late. The Civil Aeronautics Board—a precursor to the National Transportation Safety Board as the agency tasked with investigating aviation accidents—couldn’t fully explain the discrepancy in its final report. Because there were no onboard data recordings, no cockpit recordings, and no witnesses to the accident, the CAB could only cite possible explanations. These included less favorable winds than expected, course deviations around clouds, and the chance that the pilots wanted to give passengers better views of the Grand Canyon below.

In his book about the tragedy, We Are Going In, Mike Nelson, whose uncle, Jack Groshans, was killed aboard United 718, explores this prospect of sightseeing diversions in detail. He notes that even though there were areas of overcast skies in the eastern half of the canyon, where the collision occurred, from above there may have been hopes or indications of gaps in the clouds below. Both flights appeared to have been chasing such prospects, as they had both made distinct, last-minute northward changes to their paths.

The consequences of these deviations were horrific. “It was as though their ends were predestined,” Nelson writes, citing their shared delays taking off, the converging paths of their original flight plans, TWA 2’s bump to 21,000 feet cruising altitude, and their diversions north to the same square inches of Grand Canyon airspace. The CAB report speculates that the airplanes were simply flying on opposite sides of the same cloud and converged on the far side, perhaps seeing each other for just a millisecond before colliding; in fact, this was what lead investigator Jack Parshall surmised based on the slight downward pitch and the right bank angle of the United DC-7 when it struck the TWA Super Constellation.

That happened at 10:31 a.m., the exact time both aircraft were supposed to have arrived at the Painted Desert line 17 miles to the east. The collision altitude: 21,000 feet.

The TWA aircraft’s distinctive tail assembly was severed from the aircraft, instantly depressurizing the cabin and rendering the craft uncontrollable. It dove like a missile for the ground and impacted Temple Butte, a prominent formation in the eastern canyon, at more than 400 mph.

United 718 had slightly more controllability, but the tip of its left wing was mangled, reducing lift. It staggered on for just a mile before crashing into nearby Chuar Butte, copilot Harms fighting for control the whole way in. In his book, Nelson speculates that Captain Shirley of United 718 wasn’t in the cockpit at the time of the crash, probably because he was in the cabin greeting passengers. This was an airline tradition at the time, particularly on those dedicated first-class flights. Nelson’s reasoning: Shirley’s remains were among the only four successfully identified from that aircraft, so he was likely not in the front of the plane, which faced the brunt of the impact; also, his voice wasn’t heard in the background of the final radio transmission made by Harms. What’s more, that message ordinarily would have been delivered by the pilot, not the copilot.

Nelson considers it unlikely that Shirley could have done any better had he still been at the controls.

The two crash sites, which crews finally reached a day after the collision, sat a mile apart, near the intersection of the Colorado and Little Colorado Rivers. The airplanes had slammed into separate canyon walls, exploding into flames and scattering debris across craggy terrain accessible only by experienced climbers, and even they had to be brought in via helicopter. Some of the wreckage was recognizable—shredded metal, bits of seat cushions and luggage, fragmented human remains. Then there was the distinctive three-vane tail assembly from the Super Constellation. The metal bore smeared paint from the other aircraft—“witness marks” that would help investigators piece together the tragedy over the coming months.

The crash debris and victim remains had settled over two wide areas, with much of it falling into deep gullies and crevices. Though recovery crews gathered as much as possible from the site over the following months, many aircraft fragments were left at the remote and largely inaccessible site for years—some to this day.

The collision of United’s Douglas DC-7, named Mainliner Vancouver, and TWA’s Lockheed L-1049 Super Constellation—Star of the Seine—was at the time the worst-ever disaster in commercial aviation. It happened during a dramatic surge in civilian air travel, at the cusp of the coming Jet Age. Piston-powered propeller aircraft were able to stretch the speed and distances of air travel while their own obsolescence lurked on the horizon, as those faster and longer-range jet-powered airliners began to enter service.

Much of the industry’s momentum could be traced to World War II, a conflict dominated by the development and large-scale deployment of innovative new aircraft, many of which would be quickly adapted from transporting soldiers and bombs to carrying paying passengers wearing heels and drinking martinis. But the overarching civilian air travel system of the 1950s—that is, the mechanics of air traffic control and the oversight of all the airplanes flying through any particular area—couldn’t keep up with all the new planes blazing through the skies. For one thing, there were shortfalls in the federal budget that left the airlines hanging, says aviation historian Robert van der Linden, curator of air transportation at the Smithsonian’s National Air and Space Museum. Active, radar-aided control, he says, was available only around major cities, and most air traffic control systems became antiquated and susceptible to human error.

The area where the airliners collided was a region where commercial pilots were simply supposed to “see and be seen” by other aircraft. But that point on the map also happened to be among the most spectacular geological attractions on the planet, and the pilots appeared to be maneuvering to offer passengers better views. That alone wasn’t problematic, or shouldn’t have been. “Pilots were allowed to deviate from their flight paths at the pilot’s discretion to avoid weather or, in the case of this accident, fly over scenic attractions,” van der Linden says.

The accident led to congressional hearings focused on aviation safety and massive changes to how aircraft flew around the country and the world. It was an era of reform that the nation might be revisiting in modern times as well, given a recent surge in aviation accidents and close calls—including the Washington, D.C., collision in January; a FedEx cargo plane passing just 100 feet over the top of a Southwest Airlines jet in Austin in 2023; a Delta Airlines jet flipping over after a hard landing in Toronto in February; a Southwest Airlines flight aborting its Chicago landing after another aircraft crossed the runway in front of it in February; an aborted takeoff due to a similar runway crossing at New York City’s LaGuardia airport in May; and, most recently, a private jet crash in San Diego in May that appeared to involve nonfunctional runway safety technology. This list doesn’t include multiple midair collisions and close calls among small private or commuter aircraft.

These, along with revelations about antiquated technology causing a recent communications blackout at Newark International Airport, are prompting the public and the aviation industry to wonder if our air traffic control system needs to modernize far more aggressively. The FAA recently reported a shortage of 3,000 air traffic controllers.

A February headline from PBS News put it this way: “Aviation disasters and close calls have people worried about flying.”

united dc7 aircraft flying above clouds

twa super constellation grand canyon crash

The Grand Canyon crash horrified the public then, too. News spread later that day around the parking lots and visitor centers when the aircraft were reported missing in the vicinity; then the wider public found out as the aircraft transitioned from “missing” to confirmed lost. As search crews—including a team of five Swiss mountain climbers—were airlifted into the canyon to begin recovering evidence and victim remains, news crews descended on Grand Canyon Village on the South Rim and in nearby Flagstaff, Arizona, where the investigation would be headquartered.

Though flying was still expensive and a relative luxury, airlines were already lofting thousands of flights per day in the United States alone. Crashes and midair collisions were actually somewhat common amid this surge in flying—though rarely at cruising altitude—as safety steps struggled to keep up with progress. But this one, above the Grand Canyon, involving state-of-the-art airplanes and experienced crews, and with record-setting loss of life, was huge and unusual, and it shook people.

Led by Parshall, the investigative work focused on radio communications, common practices of aircraft while flying off-airways, and weather—the likely culprits for any aviation accident. But he also explored critical nuances as questions emerged not only about what led the airplanes to the same point in space and time, but also about why they couldn’t be stopped.

Why didn’t they see each other?

Among the threads investigators explored was the overall visibility from within each aircraft. At the time, cockpit windows in pressurized aircraft were notoriously small, and angles of visibility might have inhibited detection of other aircraft. They also noted a possible illusion scenario: Pilots sometimes can see objects ahead of them on a potential collision course, but the objects register no relative motion from the observing aircraft until they suddenly converge in an instant. (This is similar to the feeling of being a driver in a car stopped at a traffic light and sensing an adjacent vehicle nudging forward, but thinking it’s your own vehicle drifting backward—or vice versa.)

Investigators also looked into that question of whether crews were chasing a better view of the Grand Canyon for their premier customers, who were paying what would today cost up to $3,000 for first-class transcontinental flights.

Meanwhile, the public was growing feverish about the broader air safety system. “The incredible odds against an accident such as this occurring, and the fact that it happened in such a dramatic and terrible fashion over the Grand Canyon, focused the public’s attention on the pressing need for increased vigilance over the airways,” van der Linden says. The crash ultimately led to the creation of the Federal Aviation Agency (now the Federal Aviation Administration), which van der Linden says gave the government more regulatory authority over the nation’s airways.

In August 1957, President Dwight Eisenhower signed the Airways Modernization Act, intended to develop and modernize the national system of navigation and air traffic control facilities to serve the present and future needs of civil and military aviation. At the time of the Grand Canyon collision, the FAA says, there was a debate in Washington over whether the common civilian and military air navigation system should be the military TACAN (Tactical Air Navigation System) or the civilian VOR/DME (VHF Omnidirectional Range with Distance Measuring Equipment). The former was a more precise system used for military operations, while the latter was more affordable and readily adaptable globally. It took time to make such determinations, and there wasn’t a single authority forcing the decision.

“Airlines were delaying the purchase of navigational equipment as there was uncertainty regarding what standard would be implemented,” an FAA summary reported in hindsight. “At the time of the accident, negotiations on a compromise system were ongoing. Shortly after the collision, in August 1956, the deadlock was broken and the details of a compromise agreed upon.” The solution, dubbed VORTAC, incorporated key advantages from both systems in distance measuring and directional guidance, and it would provide a critical melding of civilian and military navigation systems.

The Grand Canyon disaster also became a lesson to the industry against trusting the odds. “When it happened, it was confidently regarded as impossible by nearly the whole populace,” Nelson, the author whose uncle died in the crash, says. Though midair collisions were indeed more frequent at the time, they typically occurred at low altitude near airports, not in high, wide-open skies. Nelson places this disaster in the same category as another familiar, and perhaps equally unlikely, transportation tragedy. “The Titanic was confidently held to be unsinkable, and then, on its maiden voyage, it sank. The world was shocked. And the world was shocked with the Grand Canyon disaster, too. No accident like it had ever happened before,” he writes.

As accident investigation methods improved, global aviation became safer and safer and safer. How safe? That conversation is ongoing, as is the broader one about upgrading current air traffic control technologies once again. The system is dated, rife with old technology, and still reliant on human intervention and oversight. A digitally based upgrade, with modern high-speed data communication systems and eventually automated tracking and collision-avoidance systems long in planning, may now arrive sooner than expected: In May, Transportation Secretary Sean P. Duffy announced an effort to radically overhaul the nation’s air traffic control system, including recruiting more air traffic controllers and upgrading networks.

Meanwhile, the site of the tragedy that spawned the first industry-wide improvement in aviation safety nearly 70 years ago remains just as inaccessible from the ground now as it was then. Only the heartiest of hikers can reach it, though technically the area is closed to the public. It became a National Historic Landmark in 2014, the first such designation to commemorate something that happened in the air.

At the ceremony, attended by Nelson, victim relatives, and others affected by the disaster, park officials unveiled a plaque. It reads: “This tragic accident site represents a watershed moment in the modernization of America’s airways leading to the establishment of the Federal Aviation Administration and national standards for aviation safety. The site possesses national significance in commemorating the history of the United States of America.”

The Potomac River collision in January 2025 was the first major incident on U.S. soil in 16 years, but to a lot of people, that 16-year stretch isn’t good enough. In 1956, mass air travel was not yet fully realized—the accident then, while tragic, somehow feels explainable. But today millions of people fly every day, every hour, and helicopters aren’t supposed to crash into planes. The investigation of that crash will take a while. But whatever the conclusion, the crash happened.

Yes, we have vastly better technology now. But inexplicably, we somehow don’t have enough air traffic controllers, not even close, nor do we have the required technology to do this job in their absence. As in the terrible quiet moments that followed the Grand Canyon crash that no one saw, it’s as if it never happened, so little have we learned from it. And so the questions haven’t changed:

Are we so smart?

Have we figured this out?

Will it happen again, and again, and again?

Ask the families of the 67 people who lost their lives in the icy Potomac River one January night, seven decades after the collision of TWA Flight 2 and United Flight 718.