<p>A supplementary instruction for the UK's manual of air traffic services adds a UAS lost link secondary surveillance radar code—A7400—to the list of special-purpose emergency codes. The instruction notes, “This conspicuous code shall be used by unmanned aerial systems/remotely piloted aircraft that have lost communications with their remote pilot and are following a pre-programmed lost link flight profile.” Operators of UAS operating beyond visual line of sight (BVLOS) within controlled airspace are required to inform air traffic services on the procedures that the UAS has been programmed to follow in the event of a loss of its command and control datalink. “In the unlikely event that a UAS displays A7400 and flies a trajectory other than that which has been briefed, controllers are to consider the UAS as flying with unknown intentions” and "they should respond in the same way as to any unknown aircraft." Mandatory addition of this code is effective on May 7, 2026.&nbsp;</p>


U.K. UAS Lost Contact Code

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U.K. UAS Lost Contact Code

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