The Pentagon has grounded all of its 51 F-35 fighter planes after a routine inspection revealed a cracked turbine blade in the engine of a test aircraft in California.
It is the second time in two months that flights of the warplane have been suspended and is another setback for the $396 billion (£261 billion) F-35 Joint Strike Fighter programme.
The Pentagon's biggest weapons programme has already been restructured three times in recent years and may face further cutbacks if Congress does not avert budget reductions due to take effect on March 1.
The F-35 programme office said it was too early to know if this was a fleet-wide issue, but it was suspending all flights until an investigation was completed.
The US is trying to shore up orders from eight foreign countries that are helping to fund development of the jet, including the UK and Australia.
Australia is expected to make a decision in the next few weeks about whether to scale back its order of 100 F-35s and buy more Boeing Co F/A-18 fighters instead.