Around 1,440 Boeing jets are being inspected in the US for a possible fuel pump problem which could cause an explosion.
The Federal Aviation Authority has ordered US airlines to inspect 1,440 of the jets to check their fuel pumps. It expects similar checks worldwide.
Britain's easyJet was one of three airlines which first discovered the problem.
The FAA estimates 1,250 pumps could have wires too close to a rotor which may chafe.
But it stresses no serious incidents have yet been linked to the pumps, which are made by Hydro-Aire of Burbank, California.
They were installed in January and April on Boeing 737s, 747s and 757s. The airlines have been given four days to inspect their fleets.
Foreign airlines operate about 2,100 of the Boeing jets. The FAA is sending advisories about the pumps to its counterpart agencies in those countries.
An FAA spokesman says any airlines with the pumps are being ordered to keep enough fuel in the tanks to cover the devices, even when the planes bank or encounter turbulence in flight. He claims the submersion will prevent any sparks from igniting fuel vapours.
Ron Wojnar, the FAA's deputy director of aircraft certification services, said: "This is not an unsafe condition."
The order affects 515 of the 737s, 247 of the 747s, and 678 of the 757s operated by US carriers. The FAA will issue a follow-up directive in a few weeks, instructing carriers to repair or replace any faulty pumps.