Britain's combat aircraft fleet is “alarmingly” low in number and would struggle to defend the UK in an all-out war, MPs have warned.
Cuts set out in the 2021 Defence Command Paper will create a combat air capability gap that will persist into the 2030s and leaves Britain dangerously exposed, the Commons Defence Committee said in a report.
The panel of MPs criticised the retirement of the C-130J Hercules transport aircraft fleet seven years before its planned out-of-service date.
The report, Aviation Procurement - Winging It, said the RAF fleet was made up of highly capable aircraft, but was short in numbers, leading to questions being asked as to whether RAF aircraft could defend the UK in all-out war.
The report also called on the Government to increase the number of combat aircraft urgently and get planned upgrades integrated into the fleet quickly.
It said the move severely reduces the capacity of the RAF's air mobility fleet to support defence operations and humanitarian missions, and could hamper the special forces in particular.
The decision to reduce the UK's fleet of Wedgetail E-7 early warning aircraft from five to three "stands out as the most perverse" of all the Defence Command Paper's cuts, the report said.
It also called delays in flying training programmes in recent years "completely unacceptable", saying years-long waits for pilots to qualify were damaging both morale and the effectiveness of the Armed Forces.
The Ministry of Defence (MOD) will spend more than £55m sending pilots overseas for fast-jet training because of a lack of aircraft availability, MPs noted.
They also said the increasing reliance on using simulators for flying training was "sub-optimal" for pilots and ground crew as it was no substitute for live flying.
Tobias Ellwood, the Chair of the Defence Select Committee, said Russia's illegal invasion of Ukraine had "signalled the beginning of a darker and more dangerous era for Europe".
"Despite this, the Ministry of Defence has failed to reverse any of its 2021 cuts to our aviation capabilities," he said.
"If the Ministry of Defence refuses to see the writing on the wall and fails to make adequate investment, there are turbulent times ahead."
Below, we look at the specific issues outlined in the report.
Hercules and Wedgetail
The report says the retirement of the Hercules fleet has severely reduced the capacity of the air mobility fleet, with particular concern regarding the UK's Special Forces.
It says the RAF will be left scrambling to transfer essential capabilities using the Atlas, which has a bad track record in terms of reliability.
The report also found reducing the UK's Wedgetail fleet from five to three stood out as "the most perverse" in the Defence Command Paper.
It saw the fleet cut by 40% for an acquisition saving of 12%, with the committee concluding this reduction would leave the UK short on both its Nato commitments and domestic needs.
The report called for the decision to be reversed and the current number of Wedgetail aircraft to be boosted by at least five.
The committee also criticises the RAF's senior leadership for not addressing the problems faced within the pilot training pipeline.
It says the delays are "completely unacceptable" and have a serious impact on the effectiveness of the UK Armed Forces and the morale of pilots.
As a result, the Committee said the training model is clearly not fit for purpose if it cannot adapt to changing crewing requirements.
Fast-jet training was singled out as an area that had particularly suffered in capacity due to a lack of available aircraft, with the MOD spending more than £50m to send pilots overseas for training as a result.
It was also noted that contractors responsible for a lack of aircraft face no financial penalty.
The report says the MOD should review any contractual arrangements and processes from the training model and make sure contractors are liable for the costs of their failures.
It also said the RAF's intention of 80% of flying training to be completed using simulators is sub-optimal for both the pilots and ground crew.
It advises that the MOD should make sure simulators and live flying training are conducted together, in line with the proposed approach taken across Nato.
Mr Ellwood said the air capability of the UK "can make or break a military".
"The ability to control the skies is critical in modern warfare and aircraft provide unparalleled reach, height and speed for our Armed Forces," he said.
"Since the end of the Cold War, the RAF's fleet has taken a nosedive in numbers, down to just a third of its previous size.
"Our report ... found that budget cuts – including those in the last Defence Command Paper – have led to gaps in air capability that will persist into the next decade.
"Our inquiry found that the RAF has prioritised quality at the expense of quantity, leaving us with a fleet of combat aircraft that are high-spec and expensive yet alarmingly low in number.
"Our current fleet fails to reach the mass necessary to survive the attrition of an all-out war with a peer adversary.
"Fixing this is a matter of urgency; allowing capability gaps to bed in will only widen them in the long-term."
The Committee has also launched a new inquiry into future aviation capabilities, examining the MOD's forthcoming procurements.
An MOD spokesperson said: "The RAF remains a world leading defence force and has the necessary capabilities to fulfil NATO and UK commitments.
"Offering 24/7 defence of the UK and protecting our overseas territories and interests, the RAF’s capabilities and people play a vital role in addressing threats rapidly and wherever they emerge in the world.
"The RAF is also spearheading transformation by investing in cutting-edge technology and modern aircraft necessary to fly and fight effectively while also rapidly addressing known challenges, such as the flying training pipeline.
"The Committee’s report recognises that the updated Defence Command Paper seeks to tackle the threats we face, now and in the future."