Flight Details
Aircraft Type: Boeing 777-222 Operator: United Airlines Registration: N791UA Flight Number: UA130 Route: Tokyo Haneda Airport (HND), Japan to Newark Liberty International Airport (EWR), USA Date of Incident: 18 April 2025 Total Occupants: 290 (passengers and crew) Weather Conditions: Cruise flight over Pacific Ocean at FL350; no adverse weather reported at time of event
Introduction
On 18 April 2025, United Airlines flight UA130 from Tokyo to Newark diverted to Anchorage after the crew detected a fuel leak from the right-hand side of the aircraft while cruising over the Pacific Ocean. The aircraft, a Boeing 777-200 powered by two Pratt & Whitney PW4090 engines, was approximately 410 nautical miles south of Anchorage when the abnormal fuel imbalance and visible signs of leakage prompted a decision to divert. The aircraft landed safely on Anchorage’s runway 15, and the right engine was shut down after landing. No injuries were reported, and the flight was subsequently cancelled. The aircraft remains grounded in Anchorage for inspection and possible repair.
Sequence of Events
Flight UA130 departed Tokyo Haneda on a long-haul transpacific route to Newark. The aircraft was established at FL350 approximately midway across the Pacific Ocean when the crew identified a significant fuel discrepancy between the left and right wing tanks, accompanied by cockpit alerts suggesting fuel system abnormalities.
Crew actions included:
Monitoring fuel quantity indicators Crosschecking EICAS alerts for fuel leak or imbalance Verifying with onboard fuel burn tracking versus expected consumption Monitoring engine parameters for abnormal performance (N1/N2, EGT, fuel flow)
At approximately 410 nautical miles south of Anchorage, the decision was made to divert. The aircraft began a controlled descent and diverted northwest toward Ted Stevens Anchorage International Airport (ANC), one of the designated ETOPS alternate airports for transpacific operations.
During descent and approach, the crew monitored engine performance and fuel leak status. The aircraft landed safely on runway 15 at Anchorage. After touchdown, the crew elected to shut down the right engine (PW4090) on the taxiway due to suspected ongoing fuel leakage and as a precautionary safety measure. The aircraft taxied to the apron on one engine, accompanied by airport emergency services.
Crew & Communication
The crew followed standard ETOPS fuel management and emergency diversion protocols. The decision to shut down the right engine after landing reflects caution in managing residual fuel leak risk and reducing potential for post-landing ignition or system failure.
There is no indication that the engine was shut down in flight, suggesting that it remained within operational parameters despite the leak. Communications with Anchorage ATC were professional and methodical, with no Mayday declaration reported—though emergency services were positioned for precautionary response.
Aircraft Systems & Technical Analysis
The Boeing 777-200 is equipped with an advanced fuel management system that distributes fuel between several tanks located in each wing, the centre section, and optional stabiliser tanks. A fuel leak in-flight is a serious ETOPS condition requiring diversion if:
Fuel loss exceeds calculated burn Fuel imbalance develops beyond safe limits EICAS messages indicate loss of containment or flow rate abnormality Visual signs (vapor trail, fluid dripping) are observed
The Pratt & Whitney PW4090 engine is equipped with integrated fuel pump, filter, and servo components. Potential leak sources include:
Fuel line rupture or joint separation Leaking fuel-oil heat exchanger (FOHE) Fuel pump casing cracks Loose or defective quick-disconnect couplings Vent or overflow system failure
Post-flight inspection will include:
External visual inspection of nacelle, pylons, and fuel lines Pressure testing of the engine fuel system Inspection of the wing tank transfer plumbing Fuel quantity system integrity check (sensors and wiring)
The fact that the engine remained operational through landing suggests no flameout, no fuel starvation, and that any leak was external rather than internal combustion-related.
Passenger Experience & Cabin Conditions
There are no reports of panic, smoke, or abnormal cabin conditions. Passengers may have been aware of the diversion, but crew communication and calm management ensured a smooth experience. Cabin pressure and environmental systems operated normally throughout the descent and landing.
Upon arrival in Anchorage, passengers disembarked via standard procedures and were offered accommodation as the remainder of the flight was cancelled. United Airlines issued a statement citing a technical fault and confirmed all safety protocols were followed.
Emergency Response & Aftermath
Anchorage airport fire and rescue units were on standby during landing. Upon arrival at the stand, a visual inspection was initiated, and maintenance crews began containment protocols to prevent environmental contamination from leaked fuel.
The aircraft was not towed and retained sufficient steering and brake function. There were no reports of fuel pooling, fire, or additional system loss. The area around the aircraft was secured to allow for inspection and defueling if necessary.
As of 24 hours post-landing, N791UA remains grounded at Anchorage pending further technical evaluation.
Investigation Status
United Airlines’ Engineering and Safety divisions have launched a full technical review, supported by Pratt & Whitney and Boeing engineering teams. The FAA has been notified of the diversion and will review the maintenance findings and determine if further regulatory action is required.
Key investigation points include:
Identification of the leak source (tank, line, or engine component) Assessment of potential safety exposure had the leak continued in-flight Evaluation of maintenance history and recent fuel system interventions Analysis of engine data, fuel flow rates, and pressure fluctuations
No preliminary indication suggests a systemic fault across the fleet, but results may guide future service bulletins or operator advisories.
Root Cause & Contributing Factors
The fuel leak’s precise origin is not yet confirmed, but likely causes include:
Mechanical failure of a fuel line connection or clamp Thermal stress cracking of components under high-pressure routing Vibration-induced wear at pylon or engine interface points Faulty O-rings or seals in a transfer valve or filter housing
Contributing factors may involve:
Extended ETOPS routing and thermal cycling Age or flight hours of the fuel system components Recent maintenance or deferred item backlog
The use of Anchorage as an ETOPS diversion airport reflects excellent planning and route risk management.
Safety Recommendations & Industry Impact
Pending the root cause findings, recommendations may include:
Increased frequency of pressure testing on PW4090 fuel systems Targeted inspection of known leak-prone joints or fittings Cross-fleet alert for any 777-200s showing similar fuel discrepancies in cruise Review of inflight fuel leak checklist steps for early detection and isolation
No known prior incidents have affected this specific aircraft registration in recent years.
Conclusion
The diversion of United Airlines flight UA130 due to a mid-Pacific fuel leak was professionally managed and executed with minimal risk to safety. The crew’s measured actions ensured the aircraft remained fully controllable and that the potentially hazardous condition was neutralised by a timely landing at Anchorage.
The event reinforces the importance of robust ETOPS procedures, precise fuel monitoring systems, and the need for vigilant engine and systems health tracking on ultra-long-haul operations.
Disclaimer
This article is based on publicly available information and reports at the time of writing. While every effort has been made to ensure accuracy, we cannot guarantee the completeness of the information provided.
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