| 1 | A | Alton R.R. | 1/1943-7/1954 | | NAKINA |
| 2 | A | Alton R.R. | Jan-52 | | NRHS |
| 3 | A | ALTON RAILROAD | | | PWRC |
| 4 | A | Alton Railroad | | | RSRV |
| 5 | A&BB | Akron & Barberton Belt R.R. | 7/1923-4/1938 | | NAKINA |
| 6 | A&BB | Akron & Barberton Belt R.R. | 7/23-4/38 | | NRHS |
| 7 | A&BB | AKRON & BARBERTON BELT RAILROAD | | | PWRC |
| 8 | A&BC | ALTOONA & BEECH CREEK RAILROAD | | | PWRC |
| 9 | A&E | ALTON AND EASTERN RAILROAD | | | PWRC |
| 10 | A&ER | ANNAPOLIS & ELK RIDGE RAILROAD | | | PWRC |
| 11 | A&GW | The Alberta & Great Waterways Ry. Co. (Northern Alberta Rys. Co.) | 7/1930-7/1936 | | NAKINA |
| 12 | A&GW | THE ALBERTA & GREAT WATERWAYS RY. CO. (NORTHERN ALBERTA RYS. CO.) | | | PWRC |
| 13 | A&K | ALLEGHANY AND KINZUA RAILROAD | | | PWRC |
| 14 | A&LM | Arkansas & Louisiana Missouri Ry. Co. (Huttig, Mansfield & Nacogdoches R.R.) | 7/1930 | | NAKINA |
| 15 | A&LM | Arkansas & Louisiana Missouri Ry. Co. | 7/1923 & 7/1932-7/1936 | | NAKINA |
| 16 | A&LM | The Arkansas & Louisiana Midland Ry. Co. | 8/1920 | | NAKINA |
| 17 | A&LM | Arkansas & Louisiana Missouri Ry. Co. | 23-Jul | | NRHS |
| 18 | A&LM | *THE ARKANSAS & LOUISIANA MIDLAND RY. CO. | | | PWRC |
| 19 | A&LM | *ARKANSAS & LOUISIANA MISSOURI RY. CO. {HUTTIG, MANSFIELD & NACOGDOCHES RAILROAD] | | | PWRC |
| 20 | A&M | Alabama & Mississippi R.R. Co. | 8/1920 | | NAKINA |
| 21 | A&M | ALABAMA & MISSISSIPPI RAILROAD CO. | | | PWRC |
| 22 | A&NE | ABBOTSFORD & NORTH EASTERN RR | | | PWRC |
| 23 | A&S | Missouri Pacific System | eliminated 1/1979 | | NAKINA |
| 24 | A&S | Abilene & Southern Ry. Co. | 8/1920-7/1954 | | NAKINA |
| 25 | A&S | Abilene & Southern Ry. Co. | 7/23-1/52 | | NRHS |
| 26 | A&S | Missouri Pacific System | eliminated 1/79 | | NRHS |
| 27 | A&S | ABILENE & SOUTHERN RY. CO. | | | PWRC |
| 28 | A&SA | Atlanta & St. Andrews Bay Ry. | 7/1923-1/1952 | | NAKINA |
| 29 | A&SA | Atlanta & St. Andrews Bay Ry. | 7/23-1/52 | | NRHS |
| 30 | A&SA | ATLANTA & ST. ANDREWS BAY RY. CO. | | | PWRC |
| 31 | A&SL | ADIRONDACK & ST LAWRENCE RR | | | PWRC |
| 32 | A&V | The Alabama and Vicksburg Ry. Co. | 7/1923 | | NAKINA |
| 33 | A&V | The Alabama and Vicksburg Ry. Co. (Illinois Central System) | 7/1930 | | NAKINA |
| 34 | A&V | The Alabama and Vicksburg Ry. Co. (Illinois Central R.R. Co.) | 7/1932 | | NAKINA |
| 35 | A&V | The Alabama and Vicksburg Ry. Co. | 23-Jul | | NRHS |
| 36 | A&V | ILLINOIS CENTRAL RR [ALABAMA & VICKSBURG RY. CO.} | | | PWRC |
| 37 | A&W | Alexandria & Western Ry. Co. | 8/1920-7/1923 | | NAKINA |
| 38 | A&W | Alexandria & Western Ry. Co. | 23-Jul | | NRHS |
| 39 | A&W | ALEXANDRIA & WESTERN RY. CO. | | | PWRC |
| 40 | A&WP | Atlanta & West Point R.R. Co. | 4/1938-10/1966 | | NAKINA |
| 41 | A&WP | Atlanta & West Point R.R. Co. | 4/38-10/66 | | NRHS |
| 42 | A&WP | ATLANTA & WEST POINT RAILROAD CO. | | | PWRC |
| 43 | A0 | Thai Jet International | ICAO: THJ, Designator A0* recalled by IATA | T | AVCODES |
| 44 | A0 | Elysair S.A.S. d/b/a L'Avion | ICAO: AVI, Merged into Openskies. IATA designator changed to EC. | F | AVCODES |
| 45 | A0 | Macair Jet S.A. | ICAO: MCJ, Callsign: Jetmac, IATA Prefix: 177, Name changed to Avian L�neas A�reas S.A. w.e.f. December 2016. IATA designator changed from IA, Designator VM recalled by IATA. | RA | AVCODES |
| 46 | A0 | Avian Líneas Aéreas S.A. t/a Avianca Argentina | ICAO: MCJ, Callsign: Jetmac, IATA Prefix: 177, ICAO designator changed to ANC. ICAO callsign changed to Avian. Name changed from Macair Jet S.A. w.e.f. December 2016. | RA | AVCODES |
| 47 | A0 | Avian Líneas Aéreas S.A. t/a Avianca Argentina | ICAO: ANC, Callsign: Avian, IATA Prefix: 177, Ceased operations on 07 June 2019. ICAO designator changed from MCJ. ICAO callsign changed from Jetmac. Name changed from Macair Jet S.A. w.e.f. December 2016. | RA | AVCODES |
| 48 | A0 | BA EuroFlyer Limited d/b/a British Airways | ICAO: EFW, New planned low subsidiary of British Airways | GB | AVCODES |
| 49 | A1 | G2 Switch Works | Designator A1 recalled by IATA. Computer Reservations Systems (CRS) | USA | AVCODES |
| 50 | A1 | A.P.G. Distribution System | Computer Reservation System | F | AVCODES |
| 51 | A2 | Cielos del Peru, S.A. | ICAO: CIU, Callsign: Cielos, IATA Prefix: 529, Founded in 1997 and started operations in 1998. On 31 January 1998, Export Air was merged into Cielos. Ceased operations. ICAO designator changed from EXD. ICAO Callsign changed from Export | RA | AVCODES |
| 52 | A2 | Cielos del Peru, S.A. | ICAO: EXD, Callsign: Cielos, IATA Prefix: 529, ICAO designator changed to CIU. ICAO Callsign changed from Export | RA | AVCODES |
| 53 | A2 | South Asian Airlines Ltd. (SAAL) | ICAO: BDS, Callsign: South Asian, IATA Prefix: 196, | BD | AVCODES |
| 54 | A2 | Astra Airlines | ICAO: AZI, Callsign: Greek Star, Ceased operations on 14 November 2019. | GR | AVCODES |
| 55 | A2 | Anima Wings Aviation S.A. | ICAO: AWG, Callsign: Anima Wings, Founded on 17 July 2019. | RO | AVCODES |
| 56 | A3 | Aegean Airlines, S.A. | ICAO: AEE, Callsign: Aegean, IATA Prefix: 390, Name changed from Aegean Aviation S.A. Merger with Cronus Airlines X5/CUS | GR | AVCODES |
| 57 | A3 | Aegean Aviation, S.A. | ICAO: AEE, Callsign: Aegean, IATA Prefix: 390, Name changed to Aegean Airlines S.A. Founded in 1987. | GR | AVCODES |
| 58 | A4 | Southern Winds, S.A. | ICAO: SWD, Callsign: Southern Winds, IATA Prefix: 242, Ceased Operations in 2005 | RA | AVCODES |
| 59 | A4 | Aerocomercial Oriente Norte Ltd | ICAO: AEK, Callsign: Aerocon, Founded in 2005. Ceased operations during 2015. | BOL | AVCODES |
| 60 | A4 | JSC Azimuth Airlines | ICAO: MUT, Callsign: Igavia, ICAO designator changed to AZO. | RUS | AVCODES |
| 61 | A4 | JSC Azimuth Airlines | ICAO: AZO, Callsign: Igavia, ICAO designator changed from MUT. | RUS | AVCODES |
| 62 | A5 | Airlinair | ICAO: ARF, Callsign: Airlinair, ICAO designator changed to RLA. Established in 1998. Commenced operations in May 1999. | F | AVCODES |
| 63 | A5 | Tikal Jets, S.A. | ICAO: TKC, Callsign: Tikal, IATA designator changed to WU*. IATA designator changed from 2E* | GCA | AVCODES |
| 64 | A5 | Airlinair | ICAO: RLA, Callsign: Airlinair, Name changed to HOP!-Airlinair w.e.f. 31 March 2013. ICAO designator changed from ARF | F | AVCODES |
| 65 | A5 | Avolar Airlines, SA de C.V. | Designator A5* recalled by IATA | MEX | AVCODES |
| 66 | A5 | HOP! | ICAO: HOP, Callsign: Airlinair, Name changed from Airlinair. ICAO designator changed from ARF | F | AVCODES |
| 67 | A5 | Hop!-Airlinair | ICAO: RLA, Callsign: Airlinair, Name changed from Airlinair w.e.f. 31 March 2013. ICAO designator changed from ARF | F | AVCODES |
| 68 | A6 | Yunnan Hong Tu Airlines Co., Ltd. | ICAO: HTU, Callsign: Hong Land, IATA Prefix: 389, Name changed to Air Travel Co., Ltd. ICAO Designator changed to OTC. | PRC | AVCODES |
| 69 | A6 | Air Travel Co., Ltd. | ICAO: OTC, Callsign: Air Travel, IATA Prefix: 389, Name changed from Yunnan Hong Tu Airlines Co., Ltd. ICAO designator changed from HTU. | PRC | AVCODES |
| 70 | A7 | Air Comet, S.A. | ICAO: MPD, Callsign: Red Comet, IATA Prefix: 352, Ceased operations on 21 December 2009. IATA designator changed from 2Z* | E | AVCODES |
| 71 | A7 | Aero Calafia, S.A. de C.V. t/a Calafia Airlines | ICAO: CFV, Callsign: Calafia, | MEX | AVCODES |
| 72 | A7 | Air Niamey, S.A. | ICAO: AWN, Callsign: Air Niamey, | RN | AVCODES |
| 73 | A8 | ARPA Aerolineas Paraguayas | ICAO: PAY, Callsign: ARPA, Merged with TAM-Mercosur in December 2002. Founded in 1994. | PY | AVCODES |
| 74 | A8 | Ameriflight, Inc. | ICAO: AMF, Callsign: Amflight, Name changed to Ameriflight, LLC w.e.f. 11 May 2005. | USA | AVCODES |
| 75 | A8 | Benin Golf Air SA | ICAO: BGL, Callsign: Benin Golf, IATA Prefix: 719, | DY | AVCODES |
| 76 | A8 | Aerolink Uganda Limited | ICAO: XAU, Designator A8* recalled by IATA | EAU | AVCODES |
| 77 | A8 | Aerolink Uganda Limited | ICAO: XAU, Designator A8* reinstated by IATA | EAU | AVCODES |
| 78 | A8 | Ameriflight, LLC | ICAO: AMF, Callsign: Amflight, Designatir A8 recalled by IATA. Name changed from Ameriflight, Inc. w.e.f. 11 May 2005. | USA | AVCODES |
| 79 | A9 | Airzena Georgian Airlines | ICAO: TGZ, Callsign: Tamazi, IATA Prefix: 606, Name changed to Georgian Airways in August 2004. Designator A9 reinstated by IATA | GE | AVCODES |
| 80 | A9 | Georgian Airways | ICAO: TGZ, Callsign: Tamazi, IATA Prefix: 606, Filed for bankruptcy on 31 December 2021. Name changed from Airzena Georgian Airlines in August 2004. Designator A9 reinstated by IATA. | GE | AVCODES |
| 81 | AA | American Airlines | ICAO: AAL, Callsign: American, IATA Prefix: 001, | USA | AVCODES |
| 82 | AA | Ann Arbor R.R. Co. | added 1/1989; 1/1994-7/2005 | | NAKINA |
| 83 | AA | Ann Arbor R.R., Michigan Interstate Ry. Co., Operator-in-Reorganization (W. Clark Durant, Ill, Trustee) | eliminated 1/1989 | | NAKINA |
| 84 | AA | Ann Arbor R.R., Michigan Interstate Ry. Co., Operator-in-Reorganization | added 4/1988 | | NAKINA |
| 85 | AA | Ann Arbor R.R. System, Michigan Interstate Ry. Co., Operator-in-Reorganization | eliminated 4/1988 | | NAKINA |
| 86 | AA | Ann Arbor R.R. Co. | eliminated 1/1978 | | NAKINA |
| 87 | AA | Ann Arbor R.R. System, Michigan Interstate Ry. Co., Operator | added 1/1978; 1/1980-1/1985 | | NAKINA |
| 88 | AA | Ann Arbor R.R. Co. (Owned and leased by the Michigan State Highway Commission) (Consolidated Rail Corp. designated operator) | added 7/1976 | | NAKINA |
| 89 | AA | Ann Arbor R.R. Co., John M. Chase, Jr., Trustee | eliminated 7/1976 | | NAKINA |
| 90 | AA | Ann Arbor R.R. Co. | 7/1932-1/1975 | | NAKINA |
| 91 | AA | Ann Arbor R.R. Co. | 4/38-1/75; eliminated 1/78 | | NRHS |
| 92 | AA | Ann Arbor R.R. System, Michigan Interstate Ry. Co., Operator | added 1/78; 1/80 | | NRHS |
| 93 | AA | Ann Arbor R.R. System, Michigan Interstate Ry. Co., Operator-in-Reorganization | eliminated 4/88 | | NRHS |
| 94 | AA | Ann Arbor R.R., Michigan Interstate Ry. Co., Operator-in-Reorganization | added 4/88 | | NRHS |
| 95 | AA | Ann Arbor R.R., Michigan Interstate Ry. Co., Operator-in-Reorganization (W. Clark Durant, Ill, Trustee) | eliminated 1/89 | | NRHS |
| 96 | AA | Ann Arbor R.R. Co. | added 1/89; 1/94-7/2000 | | NRHS |
| 97 | AA | ANN ARBOR RAILROAD | | | PWRC |
| 98 | AA | Ann Arbor Railroad | | | RSRV |
| 99 | AAA | Ansett Australia Holdings Limited | IATA: AN, Callsign: Ansett, IATA Prefix: 090, Ceased operations 04 March 2002. | AUS | AVCODES |
| 100 | AAA | Ansett Airlines of Australia | IATA: AN, Callsign: Austair, IATA Prefix: 090, Name changed to Ansett Australia Holdings Limited. | AUS | AVCODES |
