| 1 | MCA | Midcontinent Airlines, Inc. | Callsign: Heartland, ICAO callsign changed from Continair | USA | AVCODES |
| 2 | MCA | MCA Airlines Sweden AB | Callsign: Calson, | S | AVCODES |
| 3 | MCA | Muse Air Corp | Callsign: Muase Air, | USA | AVCODES |
| 4 | MCA | Midcontinent Airlines, Inc. | Callsign: Continair, ICAO callsign changed to Heartland | USA | AVCODES |
| 5 | MCA | Mediterranean Coastal Airlines Ltd. | Callsign: Coastal Clipper, | M | AVCODES |
| 6 | MCAE | MCENENY STABLE | | | SCAC4 |
| 7 | MCAF | MCARTHUR, DENNIS TRANSPORT | | | SCAC4 |
| 8 | MCAG | MAC-AGG SUPPLY INC | | | SCAC4 |
| 9 | MCAH | MCD EXPRESS INC | | | SCAC4 |
| 10 | MCAI | MOTOR CARTAGE | | | SCAC4 |
| 11 | MCAJ | MCAFEE, M J DISTRIBUTING INC USA | | | SCAC4 |
| 12 | MCAM | MUSKINGU | | | SCAC4 |
| 13 | MCAN | MONARCH CARRIERS INC | | | SCAC4 |
| 14 | MCAO | MCCONNELL TRANSPORT INC | | | SCAC4 |
| 15 | MCAR | Metrocars | City: St. Louis | F | TRAFFIC |
| 16 | MCAS | MACA SUPPLY COMPANY | | | SCAC4 |
| 17 | MCAT | MCALEXANDE | | | SCAC4 |
| 18 | MCAU | MAERSK A/S | | DK | BIC |
| 19 | MCAU | A P MOLLER | | | SCAC4 |
| 20 | MCAX | North American Car Corp. | added 7/1955; 10/1957-1/1975; eliminated 4/1975 | | NAKINA |
| 21 | MCAX | Mather Stock Car Co. | 7/1937-7/1954; eliminated 7/1955 | | NAKINA |
| 22 | MCAX | Mather Stock Car Co. | 4/38-1/52; eliminated 7/55 | | NRHS |
| 23 | MCAX | North American Car Corp. | added 7/55; 10/57-1/75; eliminated 4/75 | | NRHS |
| 24 | MCAX | (NATX) NORTH AMERICAN CAR CORP [MATHER STOCK CAR CO.] (NCCo) | | | PWRC |
| 25 | MCAY | MCNAY, RICHARD INC | | | SCAC4 |
