| 1 | NRR | Travelair d/b/a Nature Air | IATA: 5C, Callsign: Natureair, Operations were suspended by Costa Rica CAA on 12 January 2018. | CR | AVCODES |
| 2 | NRR | Natureair | | | ICAO1 |
| 3 | NRR | Nobles Rock R.R. | added 4/1994; eliminated 7/1997; added 1/2000; 7/2000-7/2005; eliminated 7/2006 | | NAKINA |
| 4 | NRR | Nobles Rock R.R. | added 4/94; eliminated 7/97; added 1/2000; 7/2000 | | NRHS |
| 5 | NRR | NOBLES ROCK RAILROAD | | | PWRC |
| 6 | NRR | Nobles Rock Railroad | | | RSRV |
| 7 | NRRA | NAVARRO FRANCO, ALFREDO | | | SCAC4 |
| 8 | NRRC | RETIRED 04-20-92 ATP [NARAGANSETT RAILWAY CO.] | | | PWRC |
| 9 | NRRF | NORTHERN REFRIGERATED TRANSPORTATION, INC | | | SCAC3 |
| 10 | NRRF | NORTHERN REFRIGERATED TRANSPORTATIO | | | SCAC4 |
| 11 | NRRM | NATIONAL RAILROAD MUSEUM | | | PWRC |
| 12 | NRRS | NORRIS, R CO INC | | | SCAC3 |
| 13 | NRRS | NORRIS, R CO INC | | | SCAC4 |
| 14 | NRRX | NOBLES ROCK RAILROAD | | | PWRC |
