The Federal Aviation Administration issued an airworthiness directive regarding the fuel quantity indicating system of the Boeing 777 aircraft. The notice follows dozens of incidents reported by operators.

The FAA said it received from operators 25 reports of discrepancies between the fuel quantity indicating system (FQIS) of a Boeing 777 aircraft and the fuel amount recorded by the refueling truck. “In at least 16 of these events, the airplanes continued with the mission; of those, 6 landed at the destination airport, and 10 had to land at a diversion airport,” the notice outlines. 

The issue only affects the central wing tank (CWT). As a consequence, insufficient fuel may be loaded for the aircraft mission while leaving the flight crew unaware of it. Within the first three hours, the fuel system reports an anomaly, prompting a reaction from the flight crew that either turns back or diverts.

As an interim action, the airworthiness directive requires “a repetitive check of the FQIS fuel quantity calculation and display of the CWT fuel quantity.” Meanwhile, the  FAA and Boeing are developing a fix to address the discrepancy in fuel readings.

The FAA estimates that 255 airplanes could be affected by the issue in the United States.