| IATA |
ICAO |
Airline
| Country
| Callsign |
| |
| UQ |
OCM |
O'Connor-Mt. Gambier's Airline |
Australia |
|
| XD |
XXD |
OAG Worldwide. |
United States |
|
| CR |
OAG |
Official Airline Guide, Inc. (OAG) |
n/a |
|
| 4B |
|
Olson Air Service, Inc. |
United States |
|
| OL |
OLT |
OLT-Ostfriesische Lufttransport |
Germany |
Oltra |
| OA |
OAL |
Olympic Airways |
Greece |
Olympic |
| WY |
OAS |
Oman Aviation Services Co. (SAOG) |
Oman |
Oryx |
| 8Q |
OHY |
Onur Air Tasimacilik A/S |
Turkey |
Onur Air |
| 1L |
|
Open Skies Inc. |
United States |
|
| OX |
OEA |
Orient Thai Airlines |
Thailand |
Orient Express |
| ZO |
OZR |
Ozark Air Lines Inc |
United States |
|
| |
|
