The UK will be "dangerously exposed" when the last remaining C-130J Hercules transport aircraft are cut, the Commons has heard.
MPs raised a Sky News report which said internal documents showed a newer type of transport plane – the Atlas A400M – is plagued by problems.
Sky added the A400M has yet to be cleared to perform all the "niche functions" of the C-130J in special forces missions, including dropping a boat out of the back of a plane for hostage rescue missions at sea.
Defence Secretary Ben Wallace pushed back against the concerns, insisting the A400M is "performing" and "on track" when it comes to being prepared for use by the special forces.
In March 2021, Mr Wallace announced the C-130J Hercules would be retired in 2023 after 24 years of service while 22 A400Ms would be part of efforts to "provide a more capable and flexible transport fleet".
Faults with Atlas aircraft
Speaking at defence questions, Labour MP Emma Lewell-Buck (South Shields) told the Commons: "Three of the four Atlas aircraft used in the evacuation of British nationals from Sudan are reported to have developed faults.
"Two-thirds of the incoming fleet is listed as unavailable and there remains no clarity the fleet can perform the niche functions our special air and boat services need.
"Hasn't the secretary of state made a mistake in pressing ahead with ditching the Hercules fleet in their favour?"
Mr Wallace replied: "I've heard these sort of tired arguments about what we really need to do is just keep the Herc and get rid of the A400."
He said the A400M "outperforms" the Hercules in most areas, telling MPs: "It's got a longer range, bigger capacity, can land in the same area, in fact, can land in shorter distance, and in Kabul, the massive evacuation of Kabul, one A400 had a fault for six hours and managed to continue on its course.
"The A400 is performing and, as far as the migration to special forces and other capabilities, that is on track, already having done jumps from it and other parts of the area.
"The simple reality is the A400 outperforms it (the Hercules), its availability was extremely successful, the Hercules only accounts for 10% of the fleet and the overall fleet for lift is now the biggest it has been for 50 years."
No loss of operational capability
Labour MP Dan Jarvis, a former soldier, later said Mr Wallace had previously given him commitments there "wouldn't be any loss of capability".
He added: "But today Deborah Haynes, at Sky News, is reporting that the UK will be left dangerously exposed when the C-130J is cut next month, and this comes amid concerns that its successor – the Atlas A400M – has yet to be cleared to perform the niche but mission-critical functions of the C-130J.
"So can I ask the minister to give an absolute assurance that our defensive procurement system will ensure there is no loss of operational capability?"
Defence minister James Cartlidge replied: "I'm more than happy to give him that assurance.
"I know there is a great affection for the Hercules but just to go back to what the secretary of state was talking about in terms of the recent performance in Sudan, it's such an important operation.
"The largest number of evacuees carried out of Sudan by the Hercules was 143. The largest number in an A400 I can confirm was around 100 more than that."