| Acronym |
Definition |
| OATS |
Oxford Air Training School. |
| Obst |
Obstruction. |
| OBS |
Omni-Bearing Selector. |
| OCH |
Obstacle Clearance Height. The lowest height above the elevation of the runway threshold or above aerodrome elevation. |
| OCA |
Obstacle Clearance Altitude. |
| OCL |
Obstacle Clearance Limit. |
| OEM |
Original Equipment Manufacturer. |
| Okta |
A measurement of cloud cover. One okta means one-eighth of the sky is covered. |
| Omega |
High accuracy, very-low frequency (VLF) long-range navigation system used principally by airliners, military aircraft and intercontinental business aircraft. |
| O/R |
On Request. |
| O/T |
Other Times. |
