The Boeing 777X is set to be delayed even further after issues have been found with the General Electric’s GE9X turbine engine.

The engine problem is not the first that Boeing has experienced on the plane, following delays to the delivery of the planes carbon fiber wings.

These issues, coupled with the grounding of the 737 Max following fatal crashes involving the aircraft earlier this year, leaves the planemaker giants with even more problems.

According to Reuters, Boeing chief financial officer Greg Smith said: “(The) long pole in the tent right now is the GE engine. There’s some challenges they are working through there on testing. So, we are having to do some re-testing, and they’re working their way through that.”

According to General Electric, the GE9X will be the most fuel efficient engine GE have ever produced. The firm has said that it will deliver 10% less fuel burn, and a 5% reduction in overall fuel consumption when fitted to widebody aircraft.

GE has yet to comment on the issue.