Britain's £11bn F35 jets can fly third of flights due to spares, pilot and engineer shortages

Britain's multi-billion pound fleet of F-35 stealth jets are only able to fly a third of their missions due to shortages in personnel and spare parts, a watchdog has warned.  

A damning report by the National Audit Office (NAO) said a lack of engineers and spare parts was 'undermining the armed forces' war fighting capability'. 

Auditors warned the impact meant the number of missions crews have been able to take on was 'approximately one third of the Ministry of Defence's targets'.

The national shortage in skilled engineers to oversee the project has ultimately led to 'fewer flying hours for pilots', the NAO report said. 

Despite the F-35s being trumpeted as 'significantly superior' to all other UK fighter jets, the £11bn already spent on the warplanes had delivered a 'disappointing return'.

The MoD began taking delivery of the spaced-aged fighters, built by US aerospace giant Lockheed Martin, in 2012 as part of a global project run from Washington. 

Operating from the Royal Navy's two new aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales, the stealth planes are among the most sophisticated ever built. 

Britain has committed to buying a total of 138 F-35B variants, of which 38 have been delivered and another ten are on order, but there is no approved timetable for buying the rest. The MoD expects its stealth jet fleet to remain in service until 2069.

Britain's F-35 fighter jets have been blighted by a shortage of spare parts and engineers 

the number of missions crews have been able to take on was 'approximately one third of the Ministry of Defence's targets, the NAO warned (file image of F-35s in the sky) 

Likewise, the Government recently revealed it would be purchasing a further 12 F-35A variants capable of carrying nuclear weapons. 

These cannot be deployed from the navy's aircraft carriers and it's unclear when Britain will purchase them. Critics have also claimed the UK would still be reliant on the US to deploy tactical nuclear weapons from the jets, should the plan go ahead. 

Despite being largely an American project,  around 15 per cent by value of each jet is manufactured in the UK, generating around £22billion in contracts for British firms.

The NAO's report said that 'due to failings of both the MoD and the global programme, the level of overall UK F-35 capability is currently lower than the MoD intended it would be by now at the time of its 2013 business case, and will be for several years'.

The NAO said: 'In our view, the capability achieved for the estimated £11billion spent to date is a disappointing return so far compared with MoD plans, even if other programme benefits have been significant.'

The auditor's review of the programme found it had been plagued by long delays. 

Plans to equip the warplanes with weapons, including the integration of UK-developed missiles, and to assure the MoD that the jets retain its stealth capabilities have been pushed back until the 2030s.

Likewise, the full delivery of the first batch of 48 aircraft is also behind schedule due to a combination of financial woes and problems with the global programme, the NAO said.

The F-35 had been taking part in drills last month in the Indian Ocean when it was forced to make an emergency landing 

In a bid to address the issues caused by a shortage of personnel and spares, the MoD reduced the flying requirement from ten hours to about 7.5 hours per month.

But despite this, the NAO report warned pilots were still not able to meet this target in March of last year. 

The NAO added it was not disclosing the actual figures on national security grounds. 

The MoD has not been able to sustainably deliver its targets for aircraft availability, resulting in flying hours below the requirement for pilots.

'The MoD's short-term affordability decisions and serious global programme delays have hindered the delivery of aircraft and other supporting capability', the report said.

There are 'major personnel shortages' across the F-35 force and 'serious gaps' in engineering roles.

The report said delivery of the first phase of 48 aircraft, due by the end of April 2026, was behind schedule partly for financial reasons and partly because of global programme delays.

The news comes after one of the UK's F-35Bs, embarked on £3.5billion HMS Prince of Wales in the Indo-Pacific, has been left stranded in India for the best part of a month after breaking down. 

The clapped-out £88m warplane was forced to make an emergency landing at Thiruvananthapuram airport, in Kerala, on June 14. 

The £88m warplane, dubbed one of the world's most hi-tech, was forced to make an emergency landing at Thiruvananthapuram airport, in Kerala on June 14

It was one of the stealth jets embarked on the Royal Navy's new aircraft carrier HMS Prince of Wales (which is pictured arriving in Singapore on June 23)

But after landing at the airport, the stealth aircraft developed an engineering issue which only British engineers could fix. 

A team of UK engineers arrived in the country this week but it's unclear when the jet will be fixed. 

The stricken jet's plight was later mocked by the Indian tourism board, which turned it into a meme, with a fake review written by: 'UK F-35B' that read: 'Kerala is such an amazing place, I don't want to leave. Definitely recommend.'

Speaking of the NAO's report, an MoD spokesman said: 'The National Audit Office's report rightly recognises the world-class capabilities of the F-35 fighter jet, as well as its significant economic benefits - including £22billion of work for UK companies, creating thousands of jobs.

'The programme continues to operate within its approved budget and the UK will have two full squadrons of F-35 fighter jets ready for deployment by the end of this year.

'We also recently announced we will purchase 12 F-35As, supporting 20,000 jobs in the UK, and join Nato's dual capable aircraft nuclear mission.'