March 12, 2026 — Washington, D.C. The Federal Aviation Administration (FAA) published Airworthiness Directive (AD) 2026-05-01 for certain Boeing 787-8, 787-9 and 787-10 Dreamliners, requiring replacement of transponder hardware to address failures caused by continuous-wave (CW) radio interference such as Morse code, military transmissions or ham radio signals. The issue risks unannounced loss of Mode S transponder function and traffic collision avoidance system (TCAS) advisories, potentially leading to mid-air collisions.
The AD, effective April 16, 2026, was prompted by reports of transponders failing to meet minimum operational performance standards, with FAA tests showing up to 90% failure rates in responding to radar interrogations amid CW interference. Affected airplanes are those identified in Boeing Alert Requirements Bulletin B787-81205-SB340065-00 RB, Issue 001, dated February 11, 2025, including line numbers 36200 through 54199 and 58200 and subsequent.
Unsafe Condition and Risks
The FAA is issuing this AD to address loss of transponder when in the presence of CW interference.
The unsafe condition could result in aircraft becoming invisible to air traffic control radar and disrupting TCAS alerts, increasing separation loss risks from other aircraft.
Required Fixes and Compliance
Operators must replace left and right integrated surveillance system processor units (ISSPUs), part numbers 822-2120-101 and 822-2120-102, with upgraded 822-2120-113 hardware, perform installation tests and repeat until successful. Compliance is required within times specified in the Boeing bulletin, using the AD’s effective date where applicable, generally up to 48 months.
The FAA has ensured that the new ISSPU hardware (i.e., replacement components) required by this AD meets the latest MOPS.
Costs and US Impact
The FAA estimates the directive affects 150 U.S.-registered airplanes, with per-aircraft costs of $53,001 ($340 labor + $52,661 parts), totaling $7.95 million for U.S. operators including United Airlines, American Airlines and Alaska Airlines. Secondary reports rounded this to nearly $8 million.
Airline and Public Comments
Public comments on the proposed rule included concerns from United Airlines and KLM on parts availability, addressed by FAA coordination with Boeing and Collins Aerospace. American Airlines sought clarification on software, while an anonymous commenter urged faster compliance. Kenya Airways requested delay, but FAA proceeded citing the need to mitigate the unsafe condition.
The flaw was reportedly exposed by ham radio enthusiasts, leading to FAA investigation, as noted in aviation media coverage.
Boeing supported the AD via service bulletins, ensuring the fix aligns with updated standards.
