| 1 | NPT | Executive Aviation Services | Callsign: Newport, | USA | AVCODES |
| 2 | NPT | Atlantic Airlines Limited t/a West Atlantic | Callsign: Neptune, Name changed to West Atlantic UK Limited w.e.f. 01 November 2017. | GB | AVCODES |
| 3 | NPT | West Atlantic UK Limited | Callsign: Neptune, Name changed from Atlantic Airlines Limited t/a West Atlantic w.e.f. 01 November 2017. | GB | AVCODES |
| 4 | NPT | Atlantic Airlines | | | ICAO1 |
| 5 | NPT | Portland Terminal R.R. Co. (Ore.) | 1/1975-7/2005 | | NAKINA |
| 6 | NPT | Portland Terminal R.R. Co. (Ore.) | 1/75-7/2000 | | NRHS |
| 7 | NPT | *NORTHERN PACIFIC TERMINAL | | | PWRC |
| 8 | NPT | +PORTLAND TERMINAL RAILROAD OF OREGON | | | PWRC |
| 9 | NPT | Portland Terminal Railroad | | | RSRV |
| 10 | NPTA | NORTH PRAIRIE TRANSPORTATION | | | SCAC4 |
| 11 | NPTC | NEWPORT TANK CONTAINERS INC | | | SCAC4 |
| 12 | NPTD | NEW POWER TRUCKING | | | SCAC4 |
| 13 | NPTE | NATIONAL PARK TRANSPORTS | | | SCAC4 |
| 14 | NPTG | NUNEZ, PEDRO TRUCKING | | | SCAC4 |
| 15 | NPTH | NEXUS PACIFIC TRANSPORT INC | | | SCAC4 |
| 16 | NPTK | NORTHERN PLAINS TRACK INC | | | SCAC4 |
| 17 | NPTN | N P TRUCKING CO INC | | | SCAC3 |
| 18 | NPTP | NATIONAL PETROLEUM TRANSPORTERS INC | | | SCAC3 |
| 19 | NPTR | NEPTUNE THRU-CONTAINER CORP | | | SCAC3 |
| 20 | NPTS | NIPOMO TRANSIT | | | SCAC3 |
| 21 | NPTU | NEPTUNE GLOBAL LOGISTICS PTE LTD | | SGP | BIC |
| 22 | NPTU | NEPTUNE LEASING, INC. | | | PWRC |
| 23 | NPTU | Neptune Leasing | | | RSRV |
| 24 | NPTU | NEPTUNE LEASING | | | SCAC3 |
| 25 | NPTV | NP TRANSPORT | | | SCAC4 |
| 26 | NPTW | NORDIC PRODUCT TANKERS A/S, | | | SCAC3 |
| 27 | NPTX | Newport Steel Corp. | added 10/1996; 7/2000; eliminated 4/2003; 7/2005 (not listed) | | NAKINA |
| 28 | NPTX | Newport Steel Corp. | added 10/96; 7/2000 | | NRHS |
| 29 | NPTX | NEWPORT STEEL CORPORATION | | | PWRC |
| 30 | NPTX | Newport Steel Corporation | | | RSRV |
| 31 | NPTY | NP TRANSPORTATION INC | | | SCAC4 |
