Certification depends on seal approval

The certification of the Boeing 777-9 is dependent on the approval of a redesigned seal for its GE9X engines. This modification is not required for the engines used in ETOPS tests but must be validated before the final approval from the Federal Aviation Administration (FAA).

FAA clarifies certification requirements

The FAA will not certify the Boeing 777-9 until it approves the new design of the intermediate seal, or "mid-seal," of its GE9X engines. This clarification, provided by an agency official to FlightGlobal on October 22, highlights the importance of this part in the certification process.

ETOPS tests do not require the seal

The modified seal does not need to be installed on the engines used during ETOPS tests, which are designed to show that twin-engine aircraft can operate safely far from alternate airports. However, the seal’s approval is still a prerequisite for the aircraft’s overall certification.

GE Aerospace identifies seal issue

In February 2026, GE Aerospace revealed it was investigating a potential durability issue with the seal. In April, the company said it had identified the cause and was working on a solution, without changing the schedule for the GE9X engine, according to Reuters.

GE Aerospace tests redesigned seal

GE Aerospace has since revised the seal design and begun producing engines with the fix. On September 17, its chief financial officer, Rahul Ghai, expressed confidence in the redesigned seal after internal tests, according to Reuters. He believed the issue would not delay the 2027 service entry of the 777X.

GE Aerospace delivers modified engines

During a quarterly results presentation on October 20, Larry Culp, CEO of GE Aerospace, stated that engines with the new seal had been delivered to Boeing since August. He said the company is aiming for approval by the end of the year, though it remains subject to FAA approval.

Certification milestones are distinct

In September, FlightGlobal reported that Boeing needed a certification plan for the seal fix before the FAA would authorize the ETOPS test program. The October clarification now explicitly separates the equipment needed for these tests from the approval required for full aircraft certification.

ETOPS capability targets 180 minutes

Boeing aims for an ETOPS capability of 180 minutes at the service entry of the 777-9. This allows the aircraft to operate on routes far from alternate airports. However, the FAA distinguishes between the technical approval of the aircraft-engine combination and the operating authorizations granted to airlines afterward.

GE9X already certified

The GE9X engine has already received FAA certification since September 28, 2020. At that time, GE Aviation announced nearly 5,000 hours and 8,000 test cycles for this certification. The current issue involves a modification to the engine and its integration with the certification of the 777-9.

Boeing remains on 2027 delivery schedule

Boeing continues to plan its first deliveries for 2027. However, the confidence expressed by GE Aerospace does not guarantee the FAA's approval timeline or the completion of the aircraft's other certification work. The redesigned seal is a necessary condition for the regulator's approval, not the final step in bringing the 777-9 to airlines.