The coalition has reversed its decision to switch the kind of fighter jet Britain's military will use on its aircraft carriers.
The F-35 Joint Strike Fighter will revert to using the short take-off and vertical landing (Stovl) configuration rather than the catapult and arrestor gear system the coalition had originally backed.
Ministers had decided in the strategic defence and security review to switch to the 'cats and traps' version of the fighter so it would be compatible with the landing gear on French and US Navy carriers.
Today defence secretary Philip Hammond said sticking with the coalition's original plan would lead to a three-year delay in the re-establishment of Britain's aircraft carrier capability, however.
"The national security council has decided not to proceed with the cats and traps conversion but to complete both carriers in the STOVL configuration," he told MPs in a Commons statement.
"When the facts change, the responsible thing to do is to examine the decisions you have made and to be willing to change your mind, however inconvenient that may be."
The cost of fitting 'cats and traps' has doubled from around £1 billion to around £2 billion, he added.
At present Britain plans on mothballing one of its two new aircraft carriers and introducing the other into active service from 2020.
Chief of the defence staff General Sir David Richards commented: "Our armed forces have a successful history of operating short take-off and vertical landing aircraft and our pilots are already flying trials in this variant of the Joint Strike Fighter alongside our US allies.
"These stealth aircraft will be the most advanced fast jets our armed forces have ever operated and I know they will do so with the greatest skill and professionalism."
Mr Hammond added that the government was committed to "doing what is right for Britain, not burying your head in the sand and ploughing on regardless as the last government all-too-often did".
Shadow defence secretary Jim Murphy said Britain faced "international ridicule" for the way it was handling its military.
"We will need to retrain and redevelop the skills carelessly cast aside just two years ago," he told the Commons.
"It is as incoherent as it is ludicrous."
Mr Murphy added that the prime minister's decisions had "cost British time, money, talent and prestige".
Mr Hammond replied: "It was their decisions that left us facing the challenges we did at the time of the strategic defence and security review."
He criticised the Labour government for ordering the carriers without buying 'cats and traps' in the first place.
"It was they who ordered the ships without having the money to pay for them, and then drove £1.6 billion of cost into the carrier programme by delaying the bill to accommodate a £250 million cash flow problem."