At least 15 Lockheed Martin F-35s are grounded for about 10 days to repack improperly installed parachutes, according to the programme office.
The grounding suspends all high-speed ground and flight tests at Edwards AFB, California; Eglin AFB, Florida and Fort Worth, Texas, the F-35 programme said.
Eight F-35s based at Naval Air Station Patuxent River, Maryland, remain flightworthy.
The grounded aircraft are equipped with new versions of the Martin Baker US16E ejection seat, the F-35 programme said.
The wrong packing instructions were sent to the ejection seat manufacturer, the F-35 programme said. As a result, Martin-Baker packed the parachutes backwards, the programme said.
The ejection seats must be sent back to Martin Baker in the UK to reverse the parachutes.
The problem only involves newer ejection seats designated as -21 and -23. The F-35Bs and F-35Cs stationed at Patuxent River have older ejection seats with parachutes that were packed correctly, the programme said.
Despite two fleet-wide grounding orders last year, the programme completed all flight tests for 2011 in mid-November, although the number of test points accomplished lagged slightly behind.