The Ministry Of Defence (MOD) has announced that five of the UK's 16 F-35B fighter jets require a replacement fuel tube after engine inspections.
It comes after the F-35 Joint Program Office (JPO) issued an enterprise-wide inspection of a fuel tube within the engine on all F-35 aircraft after a US F-35B crashed in South Carolina.
Inspections on the UK fleet of F-35Bs revealed that five of the 16 aircraft were found to be in need of a replacement fuel tube - 20% of the fleet. (Actually, 30%--Ed.)
However, 80% of the UK's F-35Bs were cleared to resume flight operations following inspection.
Meanwhile, one out of the nine operational aircraft at RAF Marham is affected by the problem.
An MOD spokesperson said: "We have concluded the inspection of all our F-35s, and the vast majority have been cleared to resume all operations.
"Flight trials are continuing from the aircraft carrier, HMS Queen Elizabeth, and the programme remains on schedule to provide our Armed Forces with a game-changing capability."
A JPO statement said the aircraft needing replacement tubes are expected to be fixed over the 'coming weeks', as the parts are 'rapidly' procured by Pratt & Whitney.
The F-35B is the UK's most advanced war plane ever, with the MOD expected to purchase 138 jets in total.
The aircraft are currently undergoing flight trials with HMS Queen Elizabeth off the coast of the United States.
The fighter jet recently made history after performing the first Shipborne Rolling Vertical Landing (SRVL) on board the aircraft carrier.