| 1 | DEC | Deltacraft Oy | IATA: 4L, Callsign: Deltacraft, Designator 4L* recalled by IATA | FIN | AVCODES |
| 2 | DEC | Deccan Cargo & Express Logistics Pvt Ltd | IATA: 3C, Callsign: Deccan Cargo, IATA Prefix: 360, | IND | AVCODES |
| 3 | DECAMP | Decamp Bus Lines | | USA | TRAFFIC |
| 4 | DECB | DEUTSCH ENGINEERED CONNECTING DEVIC | | | SCAC4 |
| 5 | DECD | DEC TRANSPORT INC | | | SCAC4 |
| 6 | DECJ | DE CARO TRUCKING CO INC | | | SCAC4 |
| 7 | DECM | DEL-CO SYSTEMS | | | SCAC4 |
| 8 | DECP | DIRECT EXPEDITED CORP | | | SCAC4 |
| 9 | DECR | DECOR N W INC | | | SCAC4 |
| 10 | DECT | DEC TRUCKING | | | SCAC4 |
| 11 | DECU | DECCAN FINE CHEMICALS INDIA PRIVATE LIMITED | | IND | BIC |
| 12 | DECX | Duval Engineering & Contracting Co. | 4/1947-10/1957; eliminated 4/1960 | | NAKINA |
| 13 | DECX | Duval Engineering & Contracting Co. | 1/52-10/57 | | NRHS |
| 14 | DECX | DUVAL ENGINEERING & CONTRACTING CO. | | | PWRC |
| 15 | DECZ | DECKER COAL CO. | | | PWRC |
| 16 | DECZ | DIRECT CHASSIS & EQUIPMENT | | | SCAC4 |
