The following list shows specific aeronautical transponder codes (typically called squawk codes), and ranges of codes, that have been used for specific purposes in various countries. Traditionally, each country has allocated transponder codes by their own scheme with little commonality across borders. The list is retained for historic interest.
Pilots are normally required to apply the code, allocated by air traffic control, to that specific flight. Occasionally, countries may specify generic codes to be used in the absence of an allocated code. Such generic codes are specified in that country's Aeronautical Information Manual or Aeronautical Information Publication. There also are standard transponder codes for defined situations defined by the International Civil Aviation Organization (marked below as ICAO).
Transponder codes shown in this list in the color RED are for emergency use only such as an aircraft hijacking, radio communication failure or another type of emergency.
Code Countries Allocated use 0000 Europe Non-discrete mode A code; shall not be used.ICAO doc 4444 & ICAO Annex 10 UK Mode C or other SSR failure US Should never be assigned. Military intercept code. Internal ARTCC subsets assigned by Enroute Safety and Operations Support. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) 0021 Germany (VFR squawk code for airspace and below prior to 15 March 2007 when replaced by the international 7000 code for VFR traffic.)UKFixed-wing aircraft (Receiving service from a ship)0022 Germany (VFR squawk code for airspace above – prior to 15 March 2007 when replaced by the international 7000 code for VFR traffic.)UKHelicopter(s) (Receiving service from a ship)0025 Germany Parachute dropping in progress.0033 UK Parachute dropping in progress. 0041–0057 Belgium Assigned for VFR traffic under Flight Information Services (BXL FIC). 0100 Australia Flights operating at aerodromes (in lieu of codes 1200, 2000 or 3000 when assigned by ATC or noted in the Enroute Supplement).Australian AIP ENR 1.6 para 7.1.4 0100–0400 US Allocated to Service Area Operations for assignment for use by Terminal/CERAP/industry/unique purpose/experimental activities. 0100–0700 US Non-discrete code assignments in accordance with FAA Order JO 7110.65, 5-2. US Also for use in oceanic airspace unless another code is assigned by ATC. 0500, 0600, 0700 US External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) 1000 Canada Instrument Flight Rules (IFR) flight below 18,000 ft ASL when no other code has been assigned. ICAO Non-discrete mode A code reserved use in mode S radar/ADS-B environment where the aircraft identification will be used to correlate the flight plan instead of the mode A code. US Used exclusively by ADS-B aircraft to inhibit mode 3A transmission. US Non-discrete code assignments in accordance with FAA Order JO 7110.65, 5-2. Also for use in oceanic airspace unless another code is assigned by ATC (US). US External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) 1100 US Non-discrete code assignments in accordance with FAA Order JO 7110.65, 5-2. Also for use in oceanic airspace unless another code is assigned by ATC. US External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) 1200 Australia Civil VFR flights in class E or G airspace. Canada, US Visual flight rules (VFR) flight standard squawk code used in North American airspace when no other has been assigned or is applicable. 1201 US Assigned via FAR 93.95 for use by VFR aircraft in the immediate vicinity of LAX. US (Visual flight rules (VFR) glider operations for gliders not in contact with ATC, through February 2012.FAA Order/Publication: 7110.65U dated 2011-ß5-18) 1202 US Visual flight rules (VFR) glider operations for gliders not in contact with ATC; effective February 2012.FAA Order/Publication: 7110.65V dated 2014-02-19 Canada Visual flight rules (VFR) glider operations for gliders not in contact with ATC; effective February 2017. 1203–1272 US Discrete 1200 series codes unless otherwise allocated (for example, 1255), designated for DVFR aircraft and only assigned by a flight service station. 1255 US Aircraft not in contact with an ATC facility while enroute to/from or within the designated fire fighting area(s).FAA order JO 7110.65U 1273–1275 US Calibration Performance Monitoring Equipment (CPME) "Parrot" transponders. 1276 US Air Defense Identification Zone (ADIZ) penetration when unable to establish communication with ATC or aeronautical facility. 1277 US VFR aircraft which fly authorized SAR missions for the USAF or USCG while enroute to/from or within the designated search area.