# List of transponder codes

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. |
| 0000 | UK | Mode C or other SSR failure |
| 0000 | US | Should never be assigned. |
| 0000 | US | Military intercept code. |
| 0000 | US | 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 5,000 feet (1,500 m) and below prior to 15 March 2007 when replaced by the international 7000 code for VFR traffic.) |
| 0022 | Germany | (VFR squawk code for airspace above 5,000 feet (1,500 m) – prior to 15 March 2007 when replaced by the international 7000 code for VFR traffic.) |
| 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). |
| 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. |
| 0100–0700 | 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. |
| 1000 | 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. |
| 1000 | US | Used exclusively by ADS-B aircraft to inhibit mode 3A transmission. |
| 1000 | 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). |
| 1000 | 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. |
| 1100 | 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. |
| 1200 | 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. |
| 1201 | US | (Visual flight rules (VFR) glider operations for gliders not in contact with ATC, through February 2012.) |
| 1202 | US | Visual flight rules (VFR) glider operations for gliders not in contact with ATC; effective February 2012. |
| 1202 | 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). |
| 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. |
| 1300 | 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. |
| 1300 | US | External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 1400 | Canada | VFR flight above 12,500' ASL when no other code has been assigned. |
| 1400 | Japan | VFR flight above 10,000' MSL when no other code has been assigned. |
| 1400 | US | External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 1500 | 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. |
| 1500 | US | External ARTCC subset. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 1600, 1700 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 2000 | Australia | Civil IFR flights in class G airspace. |
| 2000 | Canada | Uncontrolled IFR at or above 18,000 ft MSL. |
| 2000 | ICAO countries | Code squawked when entering a secondary surveillance radar (SSR) area from a non-SSR area used as uncontrolled IFR flight squawk code. |
| 2000 | EASA countries | Code that pilot shall set in the absence of ATS instructions related to code setting, unless when not receiving air traffic services. |
| 2000 | 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. |
| 2000 | US | External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 2100 | Australia | Ground testing by aircraft maintenance staff. |
| 2100 | US | Non-discrete code assignments in accordance with FAA Order JO 7110.65, 5-2. |
| 2100 | US | Also for use in oceanic airspace unless another code is assigned by ATC. |
| 2100 | US | External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 2200, 2300, 2400 | US | Non-discrete code assignments in accordance with FAA Order JO 7110.65, 5-2. |
| 2200, 2300, 2400 | US | Also for use in oceanic airspace unless another code is assigned by ATC. |
| 2200, 2300, 2400 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 2500, 2600, 2700 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 3000 | Australia | Civil flights in classes A, C and D airspace, or IFR flights in class E airspace. |
| 3000 | US | External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 3100, 3200, 3300, 3400, 3500, 3600, 3700 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 4000 | Australia | Civil flights not involved in special operations or SAR, operating in class G airspace in excess of 15NM offshore. |
| 4000 | US | Aircraft on a VFR Military Training Route or requiring frequent or rapid changes in altitude. |
| 4000 | US | Non-discrete code assignments in accordance with FAA Order JO 7110.65, 5-2. |
| 4000 | US | Also for use in oceanic airspace unless another code is assigned by ATC. |
| 4000 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 4100 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 4200, 4300 | US | 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.) |
| 4400–4477 | US | Reserved for use by SR-71, YF-12, U-2, B-57, pressure suit flights, and aircraft operations above FL600. |
| 4401–4433 | US | Reserved in accordance with FAA Order JO 7110.67 (Federal Law Enforcement). |
| 4434–4437 | US | Weather reconnaissance, as appropriate. |
| 4440,4441 | US | Operations above FL600 for Lockheed/NASA from Moffett Field. |
| 4442–4446 | US | Operations above FL600 for Lockheed from Air Force Plant 42. |
| 4447–4452 | US | Operations above FL600 for SR-71/U-2 operations from Edwards AFB. |
| 4453 | US | High balloon operations: National Scientific Balloon Facility in Palestine, Texas; and other providers, some in international operations. |
| 4454–4465 | US | Air Force operations above FL600 as designated in FAA Order 7610.4. |
| 4466–4477 | US | Reserved in accordance with FAA Order JO 7110.67 (Federal Law Enforcement). |
| 4500, 4600, 4700 | US | 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.) |
| 5000 | Australia | Aircraft flying on military operations. |
| 5000 | US, Canada | Reserved for use by NORAD. |
| 5061, 5062, 5100, 5200 | US | Reserved for special use by Potomac TRACON. |
| 5100, 5200, 5300, 5500 | US | 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.) |
| 5100–5300 | US | May be used by DOD aircraft beyond radar coverage but inside US controlled airspace with coordination as appropriate with applicable Area Operations Directorate. |
| 5400 | US, Canada | Reserved for use by NORAD. |
| 5600, 5700 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 6000 | Australia | Military flights in class G airspace. |
| 6000 | US | External ARTCC subset. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 6100 | US, Canada | Reserved for use by NORAD. |
| 6200, 6300 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 6400 | US, Canada | Reserved for use by NORAD. |
| 6500, 6600, 6700 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 7000 | ICAO | VFR standard squawk code when no other code has been assigned. |
| 7000 | EASA countries | Code that pilot shall set when not receiving air traffic services, unless otherwise prescribed by the competent authority. |
| 7000 | US | External ARTCC subset. (Block of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 7000 | Australia | Unmanned aerial vehicle in all classes of airspace and when instructed to enable transponder. |
| 7001 | France | Used in some countries to identify VFR traffic. |
| 7001 | UK | Sudden military climb out from low-level operations. |
| 7004 | UK | Aerobatic and display code in some countries. |
| 7100, 7200, 7300 | US | External ARTCC subsets. (Blocks of discrete codes except that xx00 is used as a non-discrete code after all discrete codes are assigned.) |
| 7100, 7200, 7300 | Switzerland | 7100 in Switzerland for SAR (REGA). |
| 7400 | US, UK, Australia | Unmanned aerial vehicle lost link. |
| 7500 | ICAO | Aircraft hijacking. |
| 7501–7577 | US | Reserved for use by Continental NORAD Region (CONR). |
| 7600 | ICAO | Radio failure (lost communications). |
| 7601–7607 | US | Reserved for special use by FAA. |
| 7610–7676 | US | External ARTCC subset (block of discrete codes). |
| 7615 | Australia | Civil flights engaged in littoral zone surveillance. |
| 7700 | ICAO | Emergency. |
| 7701–7707 | US | Reserved for special use by FAA. |
| 7710–7776 | US | External ARTCC subset (block of discrete codes). |
| 7776 | Europe | The Mode A code 7776 is assigned as a test code by the ORCAM Users Group, specifically for the testing of transponders. |
| 7777 | US, Germany, UK, Belgium, Netherlands | Non-discrete code used by fixed test transponders (RABMs) to check correctness of radar stations (BITE). |
| 7777 | US | DOD interceptor aircraft on active air-defense missions and operating without ATC clearance in accordance with FAA Order 7610.4. |