Lost communications procedures are a critical emergency scenario for pilots operating under Visual Flight Rules (VFR) or Instrument Flight Rules (IFR).1 These procedures are applied when an aircraft cannot comply with SERA.8035, point (a), regarding radio communication.2 Radiotelephony is the standardized voice communication between a pilot and air traffic control, aiming for clear messages despite noise or accents.3 Communications also cover datalink used by airline pilots to interact with air traffic control and other aircraft.4 As of May 1, 2025, new procedures for radio communication failure in European Union (EU) airspace include the transponder code 7601 for IFR operations if the crew encounters visual conditions and chooses to continue visually.5 Communications define rules for voice communication in aviation, based on ICAO Annex 10 and Doc 4444, including call sign structures, permitted words, and message priority.6 It also covers the technical aspects of communications, such as VHF half-duplex operation and radio wave propagation.6

When an aircraft cannot comply with SERA.8035, point (a), the flight crew must try to establish contact on the previous channel and, if unsuccessful, on another appropriate channel.2 If these attempts fail, the flight crew must use all available means to contact the appropriate air traffic services unit, other air traffic services units, or other aircraft.2 Once communication is re-established, the flight crew must report that contact on the assigned channel could not be made.2 Air traffic controllers call aircraft on suspected frequencies if expected communication is not received or if requested by other units.2 For surveillance service, controllers determine if the aircraft's receiver works and continue service using SSR code/ADS-B transmission changes or IDENT transmissions for clearance acknowledgements.2 If air traffic control unit attempts fail, they request assistance from other units and aircraft on the route to call the aircraft and relay messages.2 Blind transmission of air traffic control clearances is only made at the originator's specific request if other units and aircraft fail.2 The UK Civil Aviation Authority (CAA) is not adopting certain new EU procedures for radio communication failure that took effect from May 1, 2025, and UK air traffic services personnel should be aware that international flight crews might mistakenly follow EU procedures within UK airspace.5

During a flight, the Pilot Monitoring handles communication with air traffic control. Undertaking specific radiotelephony instruction, which includes practical exercises with an air traffic controller, may decrease the quantity of extra flight hours needed during costly flight instruction. For the Private Pilot Licence (PPL), radiotelephony exercises ought to commence on the ground through role-playing scenarios, with the instructor progressively increasing the demands as the student advances.