General Electric Company (NYSE:GE) and The Boeing Company (NYSE:BA) warned airlines on Thursday about a potential problem with engines in Boeing’s 777 jumbo jet that caused engines to fail mid-flight twice this year.

A total of about 70 planes were affected by about 118 transfer-gear boxes made between September and March. About 25 of the 777-300ER jets are in service while the additional 44 are in production, a GE spokesman said. At least one plane has already been repaired.

“We’re moving very, very quickly just to make sure there are no problems,” Rick Kennedy, a spokesman for GE aviation, said in a phone interview.

He said the issue seems to be an anomaly in the metal that caused gears to separate, though the cause of the problem remains unknown. An engine first shut down mid-flight in February. Then, it happened again to another plane earlier this month.

The part, made by the GE-owned Italian company Avio SpA, has been in use since the late 1990s.

Kennedy said the company has urged airlines to run diagnostic tests on all planes carrying the part. If a plane carries the faulty part on two engines, one must be replaced, he said. If the part is on one engine, it must undergo tests before each flight to ensure safety.