| 1 | WLO | Willowair Ltd. | Callsign: Willowair, | GB | AVCODES |
| 2 | WLO | Waterloo R.R. Co. | 10/1957-1/1980; eliminated 4/1986 | | NAKINA |
| 3 | WLO | Waterloo Ry. Co. | added 4/1986; 1/1994-7/2005 | | NAKINA |
| 4 | WLO | Waterloo R.R. Co. | 10/57-1/80; eliminated 4/86 | | NRHS |
| 5 | WLO | Waterloo Ry. Co. | added 4/86; 1/94-7/2000 | | NRHS |
| 6 | WLO | WATERLOO RAILWAY COMPANY | | | PWRC |
| 7 | WLO | Waterloo Railway | | | RSRV |
| 8 | WLO | WATERLOO RAILWAY COMPANY | | | SCAC4 |
| 9 | WLO | Waterloo Railway Company | | USA | TRAFFIC |
| 10 | WLOA | WILLIS LOGISTICS | | | SCAC4 |
| 11 | WLOB | WEDGEPORT LOBSTERS LTD | | | SCAC4 |
| 12 | WLOC | WHITESTONE LOGISTICS | | | SCAC4 |
| 13 | WLOC | Miejskie Przedsiębiorstwo Komunikacyjne we Włocławku | | PL | TRAFFIC |
| 14 | WLOD | WORLD LOGISTICS INC | | | SCAC4 |
| 15 | WLOG | WALLER LOGISTICS INC | | | SCAC4 |
| 16 | WLOI | WESTONE LOGISTICS | | | SCAC4 |
| 17 | WLOJ | WHEELS LOGISTICS | | | SCAC4 |
| 18 | WLOL | WALLACE OIL COMPANY | | | SCAC4 |
| 19 | WLOM | WELLOCK, MIKE TRUCKING INC | | | SCAC4 |
| 20 | WLOP | WILSON TRANSPORT | | | SCAC4 |
| 21 | WLOQ | WOLVERINE LOGISTICS | | | SCAC4 |
| 22 | WLOR | WILSON OIL COMPANY | | | SCAC4 |
| 23 | WLOS | WALLS, OTIS A | | | SCAC4 |
| 24 | WLOT | WATERLOO TRANSPORT INC | | | SCAC4 |
| 25 | WLOY | WALTHERS OIL COMPANY | | | SCAC4 |
