F-35: BAE Systems faces turbulent times over carriers
The Ministry of Defence has confirmed it is reviewing parts of the programme to build two new aircraft carriers for the Royal Navy, throwing doubt over the planned use of the Lockheed Martin F-35 fighter plane.
This decision could have a major impact on BAE Systems, which is involved in the aircraft's development.
The cost of the two new Queen Elizabeth class carriers - originally ordered under the last Labour government - has already risen dramatically from £3.5bn to around £7bn.
Changes ordered by the coalition government could see those costs rise even further.
The current confusion is over which planes should fly off the new carrier.
Labour had originally proposed to buy a vertical landing variant of the new Joint Strike Fighter plane, also know as the F-35, which would be launched from a "ski jump" fitted on the new carriers and then land vertically.
The system is similar to that used by the Harrier jump jet on HMS Ark Royal - both of which were scrapped following the strategic defence and security review.
However, as a result of that review, the current government said it would change its F-35 order to the carrier variant.
It would though require significant modifications to the design of the aircraft carriers.
This would require the ships to be fitted with catapults and arrestor gear - or "cats and traps" - to launch and recover the planes.
At the time of the change, Prime Minister David Cameron said that the last government got it "badly wrong" on the decisions made for the new carrier.
Speaking in the Commons on 19 October 2010, Mr Cameron said Britain would now fit "cats and traps" to just one of the carriers.
He said: "This will allow our allies to operate from our operational carrier and it will allow us to buy the carrier version of the [F-35] Joint Strike Fighter which is more capable, less expensive, has a longer range and can carry more weapons."
Since then there have been a number of issues likely to have forced the rethink. The costs of fitting "cats and traps" are believed to have risen significantly.
The plan was to use the latest electro-magnetic technology to launch the planes, rather than the traditional steam catapult. But the new technology is untried and untested on board a ship.
It is due to be fitted to the next generation of US carriers, but alreadythe US Congress has voiced concerns about the programme..
The former Defence Secretary, Liam Fox, initially estimated it would cost in the region of £700m to fit the new cats and traps. The BBC understands that figure has risen to well over £1bn.
There have also been concerns over the carrier variant of the F-35.
US Department of Defence documents leaked earlier this year found that a design flaw in the fighter resulted in repeated failures during simulated landings.
Problems with the tail hook on the jet meant it failed to catch the arrestor cable on the carrier's deck to bring it to a halt.
As a result the US has postponed its order to allow more time for testing.
The UK government says it will make a final decision on which plane to buy around Easter.
But in a statement the Ministry of Defence confirmed that it's now "reviewing all programmes, including elements of the carrier strike programme, to validate costs and ensure risks are properly managed".
That review is likely to have a major impact on BAE Systems, which is the main contractor on the construction of the two new carriers, and also a partner in the development of the Joint Strike Fighter.
Though the US defence firm Lockheed Martin is the main contractor, BAE is building the tail section of all three variants of the F-35, accounting for about 10% of the work.
At Warton in Lancashire, BAE test pilots and engineers have already begun work on the new design.
They are using a sophisticated simulator that will help train pilots and allow engineers to tweak the design of the carrier.
Another change of mind will mean wasted time, money and effort.
Shadow defence secretary Jim Murphy says "the country deserves urgent clarity from the government" on this issue.
"We need to know how carrier strike capability will be delivered, with detail costs, timescales and interoperability with allies".
The decision to sell the Harriers to the US now appeared "increasingly reckless", he said.
The uncertainty cannot be entirely blamed on the government. It is not alone in facing difficult choices about the new F-35 plane.
With defence budgets shrinking around the globe, the aircraft's rising costs and technical issues still to overcome, a number of nations are reviewing their original orders for the aircraft.
The UK itself had originally planned to buy around 160 of the jets for the Royal Navy and RAF. That number has since been cut to just over 130 and could fall even further.
This government has described the state of the defence budget left by the last Labour government as a "car crash".
Ministers have promised to rein in spending and clamp down on the huge overspends that have plagued the MoD in the past.
They appear to have made some progress. But the carrier programme is still a cause for concern.