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The FAA proposes to adopt a new airworthiness directive (AD) for all Bombardier Model BD-100-1A10 aircraft, the platform behind the Challenger 300, 350 and 3500. The proposed AD is not a redesign or immediate maintenance but instead a redefining of how crews react when a specific alert appears in the cockpit.The proposal follows reports of pitch upset events. According to the FAA, EICAS messages can indicate that the autopilot is holding significant nose-up or nose-down elevator force. Delays in responding, and failure to stabilize airspeed, can leave the horizontal stabilizer severely out of trim. Disconnecting the autopilot in that state could cause a sudden elevator movement if the control column is not held firmly. The proposal would revise the Airplane Flight Manual (AFM) and move the AP STAB TRIM FAIL procedure, which covers the autopilot failing to trim the stabilizer, from a non-normal procedure to an emergency procedure. The goal is to provide crews with immediate procedures to stabilize airspeed before stabilizer trim conditions become more severe.While the FAA estimates compliance at $85 per aircraft, operators may have additional internal costs associated with reviewing procedures, updating training materials, and familiarizing crews with the revised guidance. The FAA specifically notes that operators are already required to furnish AFM revisions to pilots and ensure crews are familiar with those procedures, and that training on updated AFM content is recorded in each pilot's training record. For Part 91 flight departments, the practical work may begin well before any final rule takes effect. Training managers will need to evaluate whether current training adequately addresses the scenario described and whether pilots understand the relationship between airspeed management, stabilizer trim and autopilot disconnect events.Why it mattersThe FAA calls the proposal an interim action, the same label Transport Canada put on its own AD last year, and says it might consider further rulemaking if a final action is later identified. For operators, that creates uncertainty beyond the current flight manual revision. If future investigations or operational experience show that procedural changes alone are not reducing the risk, additional requirements could follow. The proposal already covers all 680 U.S.-registered BD-100-1A10 airplanes, sold as the Challenger 300, 350 and 3500, so any follow-up action would presumably address the same fleet. Comments are open until Oct. 29 through Docket FAA-2026-8808.