In its defence review in 2010, the coalition announced that it was cancelling the previous Labour government's decision to purchase jump-jet version of the Joint Strike Fighter (the F35-B) and opt instead for the catapult and trap (F35-C) type, which required a different set-up on deck.

BBC: Joint Strike Fighter planes (file pic)

But, in May this year, it performed a U-turn, saying it would revert to the F35-B, as costs had increased.

BBC: Joint Strike Fighter planes (file pic)

It says the US - which is leading the F35-B project - is likely to cancel its orders, as Washington struggles with a government debt crisis.

BBC: Joint Strike Fighter planes (file pic)