The US-designed fighters picked by Britain to equip its two new aircraft carriers and several RAF squadrons are facing a budget battle in the US Congress.
The US-designed fighters picked by Britain to equip its two new aircraft carriers and several RAF squadrons are facing a budget battle in the US Congress, which could wreck the timetable for their entry into UK service or even force selection of another jet.
Some American politicians are also claiming that the numbers of F35 Joint Strike Fighters (JSF) wanted by the US Air Force, Navy and Marine Corps will have to be slashed to keep the project within acceptable cost levels.
While the UK has an option on 150 of the short-take-off-vertical-landing version, no-one yet knows what the unit price of the aircraft will be. Projected support cost estimates have nearly doubled in recent years, from £230bn in 2005 to £430bn now.
All US defence programmes are facing detailed scrutiny due to the expense of the wars in Iraq and Afghanistan and the impact of the credit crunch on the US economy.
US Congressional investigators now claim that the entire F35 programme will slip by at least two years and that the £200bn overall bill for 2443 jets will rise by at least another £20bn in the interim.
The US Air Force version will replace the service's F-16 and A-10 aircraft. A short takeoff and vertical landing version will replace the Marine Corps Harrier jets and may equip the Royal Navy.
A number of US Allies - notably the UK and Norway - have signed agreements for options on at least 646 additional aircraft, dependent on price and delivery schedules.
Late-maturing technologies and weight increases in the aircraft have slowed production and forced redesigns, while difficulties in wing and final assembly phases meant that the first test aircraft required 35% more labour hours than expected.
In addition, electrical malfunctions and parts failures in prototype aircraft have delayed flight tests. "A fully integrated, capable production aircraft is not expected to enter flight testing until fiscal year 2012," the US General Accounting Office said.
Lockheed Martin, the corporation designing and building the JSF, denies that there are major development problems with the F35 and has now launched a hard-sell, comparing the stealth jet to a "racehorse" capable of many missions.
The British MoD refuses to be drawn on definite numbers to be acquired. A spokesman said a final decision would be taken "once the final unit price is known and our defence requirements assessed".
