A new report says the Ministry of Defence (MOD) is training far fewer pilots than it needs.
The National Audit Office (NAO) probe found that in the six years to 2018/19, the MOD failed to meet its training needs by an average of 45%, equating to a shortfall of 125 aircrew a year.
The NAO investigation found training has taken longer in the last two years because the MOD does not have the capacity to handle the number of students it needs to train.
In July this year, there were 145 RAF students waiting an average of 90 weeks to start training, compared to an expected 12-week wait for around 26 students at a time, while 12% of planned training courses as of March 2019 had been cancelled.
The report recognised the MOD's longstanding issues with flying training and efforts to address the shortfalls.
"The RAF cannot get enough planes in the air on the required days, the contractors cannot get their planes in the air on the right days, runways seem to be closed to be repaired, there is not enough instructors and air traffic controllers," said Defence Analyst Tim Ripley.
Under the 2010 Strategic Defence and Security Review, the MOD halved its aircrew requirement before increasing the training requirement in the subsequent 2015 review, while in 2018/19 alone, the requirement increased by 29%.
An MOD spokesman said: "The Military Flying Training System (MFTS) is the biggest transformation of UK military aircrew training in a generation and we welcome the NAO report on this programme.
"Although we acknowledge there have been some challenges, the transition to the new system is now well underway and a steady improvement in aircrew throughout is being seen in all areas."
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One major cause of the current situation is the required demand for pilots.
The Strategic Defence and Security Review of 2010 envisaged fewer pilots, but the 2015 iteration upped the numbers significantly and the system was not set up for this.
"It produces a vicious circle of shortages of people," said Mr Ripley, adding that it impacts upon satisfaction and retention rates.
"It means they need to recruit more and train more, which they cannot do," he explained.
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