FAA Finalises AD to Resolve A350 Flight-Control Hazard

WASHINGTON, D.C. — The Federal Aviation Administration (FAA) has issued a final rule, Airworthiness Directive (AD) 2025-25-12, aimed at eliminating a critical "runaway" flight control hazard affecting the Airbus A350-900 and A350-1041 fleets. The directive, published today, December 29, 2025, mandates the installation of new flight-control software to prevent uncommanded surface movements that could lead to a loss of aircraft control.

The ruling is the culmination of a global safety investigation into Flight Control Remote Modules (FCRMs). Regulators discovered that hydraulic fluid could leak into these modules, contaminating electronic circuit cards and potentially triggering catastrophic "runaway" signals to the rudder and elevators.

The Permanent Fix

Previously, the FAA and the European Union Aviation Safety Agency (EASA) relied on interim measures that required the physical inspection and frequent replacement of FCRMs; a process that cost airlines upwards of $111,276 per aircraft.

This final AD shifts the burden to a software-based solution, which the FAA identifies as the permanent terminating action. Effective January 13, 2026, all operators must upgrade their Flight Control and Guidance System (FCGS) to the following standards:

• Primary Computer (PRIM): Software standard P14.1.3
• Secondary Computer (SEC): Software standard S14.1.2

Impact on U.S. Operators and Fleet Costs

The directive primarily affects Delta Air Lines, the sole major U.S. carrier currently operating the A350. The FAA estimates that 39 U.S. registered aircraft are impacted by the order.

While the previous hardware-focused mandates were financially draining, the software patch is significantly more economical, estimated at roughly $2,234 per aircraft in labour costs. However, the cumulative exposure for the U.S. fleet since the start of the investigation exceeds $4.4 million.

2026 A350 Operational Outlook

As Delta and international partners like Virgin Atlantic and Qatar Airways implement the final software patch in early 2026, the A350 remains the backbone of long-haul recovery. Below are key representative routes for the Winter 2025/Spring 2026 season featuring the A350 fleet.

Technical Background

In a fly-by-wire aircraft like the A350, the pilot's inputs are translated by computers into electronic signals sent to actuators. A "runaway" occurs when a control surface (like the rudder) moves to its maximum limit without a command from the pilot.

The FCRM contamination issue was particularly dangerous because:

• It could bypass standard pilot overrides.
• The rudder and elevator units share a common design, meaning a single contamination source could affect multiple axes of flight.
• The software fix introduces a "reasonableness check" logic that detects erroneous FCRM signals and shuts down the compromised module before it can move the flight surface.