CINCINNATI- GE Aerospace says a redesigned mid-seal for the GE9X engine should not delay the Boeing 777X beyond the company’s existing 2027 target. Lufthansa (LH) is among the launch customers awaiting the Boeing 777-9.
The engine maker says it has completed internal testing of the redesigned component and has begun shipping GE9X engines with the new seal to Boeing. Boeing 777-9 certification work is continuing, although the program still has major testing milestones ahead.
Redesigned GE9X Seal Moves Toward FAA Approval
GE Aerospace identified a durability problem with the GE9X mid-seal after a crack was discovered during a January 2026 shop visit involving a 777X flight-test engine. The company subsequently identified the root cause, redesigned the component, and prepared its production system for the modified seal.
GE Chief Financial Officer Rahul Ghai said the company has a high level of confidence in the redesigned component following internal testing. Engines fitted with the new seal began shipping to Boeing during the third quarter of 2026.
The redesigned seal still requires Federal Aviation Administration approval. GE expects that certification process to progress over the next few months.
The existing and redesigned seals are following separate certification paths. The current component remains available for certification activities already underway on the 777X, while the redesigned production seal is undergoing its own FAA approval process.
This approach allows Boeing to continue its current certification campaign rather than waiting for the production configuration to receive approval.
GE9X Mid-Seal Issue Dates Back to Early 2026
The durability concern emerged in January 2026 when GE found a crack during a shop visit involving a GE9X installed on a 777X flight-test aircraft.
GE publicly disclosed that it was studying a potential durability issue in February. By April, the company said it had identified the root cause and was finalizing a modification.
The development timeline has since moved into production. GE started shipping engines equipped with the redesigned seal to Boeing during the third quarter of 2026.
On September 17, Ghai said the company had tested the redesign internally and was working with the FAA on certification. He said GE had enough confidence in the design to incorporate it into the engines it is currently producing.
GE previously said the issue had not changed its schedule expectations. CEO Larry Culp stated in April that there was no change to the 777X schedule while the company worked on the redesign, modified tooling, and prepared suppliers for production.
Why the GE9X Is Critical to the 777X
The GE9X is the exclusive engine for the Boeing 777X family, making its development directly linked to the aircraft program.
The engine received FAA certification in September 2020 and uses a 134-inch, or 3.40-meter, fan with 16 carbon-fiber composite blades. It belongs to the 100,000-pound-thrust class and generated 134,300 pounds of thrust during a 2017 engineering test.
GE designed the engine with several advanced technologies, including ceramic-matrix composites, additive-manufactured components, and a composite fan system. The design aims to deliver the thrust required by the large 777X while improving fuel efficiency.
GE has more than 1,000 GE9X engines on order, highlighting the scale of the production program.
The company has also conducted extensive durability testing during development. Previous testing included dust-ingestion trials intended to simulate harsh operating environments, with 1,600 test cycles completed before teardown inspection.
GE9X Key Specifications
| Specification | Detail |
|---|---|
| Aircraft family | Boeing 777X |
| Engine supplier | GE Aerospace |
| Supplier position | Sole source |
| Fan diameter | 134 inches / 3.40 meters |
| Fan blades | 16 carbon-fiber composite blades |
| Thrust class | 100,000+ pounds |
| Record test thrust | 134,300 pounds |
| High-pressure compressor ratio | 27:1 |
| FAA engine certification | September 28, 2020 |
| Engines on order | More than 1,000 |
Boeing 777X Certification Remains the Bigger Challenge
Resolving the GE9X seal issue does not mean the Boeing 777-9 is close to completing its certification program.
Boeing said in July 2026 that its 777X test fleet had accumulated more than 4,800 flight hours across approximately 1,700 flights. However, only about 50% of the planned certification testing had been completed at that point.
Most Type Inspection Authorizations had been granted, but TIA 5 and the ETOPS-focused TIAs remained outstanding.
ETOPS testing is particularly important because it is among the major certification activities still ahead. GE’s current position is that the existing GE9X mid-seal can support the certification work needed to reach that stage.
Boeing has also completed the first flight of Lufthansa’s first production 777-9. That aircraft features a fully outfitted customer cabin and will take part in additional certification and systems testing.
Boeing 777-9 Certification Status
| Certification Metric | July 2026 Status |
|---|---|
| Flight-test hours | 4,800+ |
| Test flights | Approximately 1,700 |
| Planned certification testing | Approximately 50% complete |
| Type Inspection Authorizations | Majority granted |
| Major TIAs remaining | TIA 5 and ETOPS-focused TIAs |
| Full-scale fatigue testing | More than one aircraft lifetime completed |
| Major upcoming activity | Approval for ETOPS demonstrations |
| First delivery | Anticipated in 2027 |
777X Still Targeted for 2027
Boeing continues to target the first 777-9 delivery in 2027. The aircraft program has faced repeated schedule changes since the 777X first flew in January 2020.
Reuters previously reported that the program was around six years behind schedule and had accumulated approximately $15 billion in charges. Earlier engine-related problems also affected the aircraft’s development.
The latest GE9X issue therefore attracted attention because the engine is the sole powerplant available for the 777X. A major unresolved engine problem could have affected the aircraft’s wider certification and production timeline.
GE’s latest update indicates that the redesigned seal is progressing through its FAA approval process while production engines are already being shipped to Boeing.
Airlines Await the 777X
The 777X program has significant importance for airlines that have committed to the aircraft. Boeing says customers have ordered more than 620 aircraft across the 777X family.
Extended delivery timelines have required airlines to adjust fleet plans and retain existing widebody aircraft for longer.
For the 777-9, the latest GE9X update removes the redesigned mid-seal from the list of issues that GE currently expects to affect the 2027 timetable. However, the aircraft still has substantial FAA certification work to complete before it can enter passenger service.
The next important steps include FAA approval of the redesigned GE9X seal, continued 777-9 certification testing, and progress toward ETOPS demonstrations.
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