FAA Finalizes A350 Software Mandate to Address Flight-Control Risk

The Federal Aviation Administration has finalized a new Airworthiness Directive requiring operators of all Airbus A350-900 and A350-1000 aircraft to install updated flight-control software to eliminate the risk of control-surface malfunctions linked to hydraulic fluid contamination inside key electronic components.

The directive, designated AD 2025-25-12, addresses findings that hydraulic fluid contamination of Flight Control Remote Module (FCRM) electronic cards can lead to uncommanded flight-control surface movement. Because the elevator and rudder systems share common design features, regulators determined that both systems are susceptible to the same failure mode, prompting a fleet-wide preventive action.

The FAA said the finalized rule establishes a software-based solution as the permanent corrective measure, formally ending interim hardware replacement requirements and aligning U.S. oversight with Airbus’ long-term mitigation strategy.

The directive becomes effective January 13, 2026, and supersedes an earlier interim AD that required operators to inspect and replace contaminated FCRMs after several units were found to have been exposed to hydraulic fluid during manufacturing. One such event involved a loss of control of an outboard aileron surface, which triggered the original safety action.

Under the permanent fix, Airbus has upgraded the Flight Control and Guidance System to PRIM software standard P14.1.3 and SEC standard S14.1.2. According to the FAA, the updated software prevents the unsafe failure condition and formally terminates the requirement for recurring module replacements.

The Global A350 Fleet Impact

The FAA said the directive applies to 39 U.S.-registered Airbus A350 aircraft. Delta Air Lines is the largest U.S. operator of the A350 family, the fifth-largest A350 operator globally, and the first North American airline to introduce the A350-900 into service. Delta currently operates 38 A350-900 aircraft and has six additional A350-900s and 20 A350-1000s on order.

FAA cost estimates indicate that the required software upgrade will cost approximately US$2,234 per aircraft in labor and parts. By comparison, the previously mandated hardware replacement work carried a potential cost of up to US$111,276 per aircraft. The agency estimates total potential cost exposure for U.S. operators at more than US$4.4 million.

The FAA issued the final rule without prior public comment, citing the need to promptly mitigate the risk that an uncommanded elevator or rudder movement could result in loss of aircraft control.

The directive incorporates by reference European Union Aviation Safety Agency AD 2025-0197R1 and prohibits the installation of earlier software versions once the modification is completed. Operators must comply unless the required software upgrade has already been accomplished.

Outside the United States, the Airbus A350 is widely operated by major network carriers across Europe, the Middle East, and Asia-Pacific, where the aircraft plays a central role in long-haul and ultra-long-haul operations. European operators include Lufthansa, Air France, British Airways, and Finnair, while Middle Eastern carriers such as Qatar Airways, Etihad Airways, and Emirates (A350-900 on order) rely on the type for high-capacity intercontinental routes. In Asia-Pacific, leading A350 operators include Singapore Airlines, Cathay Pacific, Japan Airlines, All Nippon Airways, Korean Air, and China Airlines. For these operators, the FAA and EASA-mandated software update is expected to be incorporated into routine maintenance planning, minimizing operational disruption while ensuring consistent compliance across global A350 fleets.

Sources: AirGuide Business airguide.info, bing.com, airwaysmag.com