| 1 | MSO | Aerolineas Mesoamericanas, S.A. de C.V. | Callsign: Meso Americanas, | MEX | AVCODES |
| 2 | MSO | Aerolineas Mesoamericanas, S.A. de C.V. d/b/a ALMA de Mexico | IATA: C4, Callsign: Alma, IATA Prefix: 665, Founded in 2005. Commenced operations on 12 June 2006. Ceased operations on 07 November 2008. | MEX | AVCODES |
| 3 | MSO | Aerolíneas Mesoamericanas | | | ICAO1 |
| 4 | MSO | Michigan Southern R.R., Inc. | added 4/1991; 1/1994; eliminated 1/1998; 7/2000-7/2005 | | NAKINA |
| 5 | MSO | Michigan Southern R.R., Inc. | added 4/91; 1/94; eliminated 1/98; 7/2000 | | NRHS |
| 6 | MSO | MICHIGAN SOUTHERN RAILROAD COMPANY, INC. | | | PWRC |
| 7 | MSO | Michigan Southern Railroad | | | RSRV |
| 8 | MSO | MICHIGAN SOUTHERN RAILROAD CO INC | | | SCAC4 |
| 9 | MSO | Mittal Steel Ostrava a.s. | | CZ | VKM |
| 10 | MSOC | MOSS OIL CO INC | | | SCAC4 |
| 11 | MSOE | MORRIS OIL CO LLC | | | SCAC4 |
| 12 | MSOG | MSA LOGISTICS | | | SCAC4 |
| 13 | MSOI | MORONI AND SON OIL LLC | | | SCAC4 |
| 14 | MSOJ | MIDNIGHT SUN OUTFITTING | | | SCAC4 |
| 15 | MSOK | MASSON TRUCKING, INC | | | SCAC1 |
| 16 | MSOK | MID-SOUTH TOWING & TRUCKING LLC | | | SCAC4 |
| 17 | MSOL | M & S TRUCKING | | | SCAC4 |
| 18 | MSOM | MCSHANE OIL | | | SCAC4 |
| 19 | MSON | MINOS SOCIETA DI NAVIGAZIONE SRL | | | SCAC4 |
| 20 | MSOO | MASON, | | | SCAC4 |
| 21 | MSOQ | MIDSTATE CONTAINERS INC | | | SCAC4 |
| 22 | MSOR | MID SOUTH CONTRACTORS | | | SCAC4 |
| 23 | MSOS | Przedsiębiorstwo Komunikacji Miejskiej w Sosnowcu | | PL | TRAFFIC |
| 24 | MSOT | MID-SOUTH TANK LINES LLC | | | SCAC4 |
| 25 | MSOU | M/S CONTAINERS A/S | | DK | BIC |
| 26 | MSOW | MARIO AND SON TRUCKING | | | SCAC4 |
| 27 | MSOY | M & S OIL COMPANY | | | SCAC4 |
