| Term | Definition / Meaning / Stand for |
| OUD |
Angads Airport (Oujda, Morocco) |
| OVD |
Asturias Airport (Spain) |
| ORD |
Chicago O'Hare International Airport |
| ORK |
Cork Airport (Ireland) |
| OTR |
Coto 47 Airport (Costa Rica) |
| ODB |
Córdoba Airport (Spain) |
| OPO |
Francisco Sá Carneiro Airport (Porto, Portugal) |
| OOL |
Gold Coast Airport (Australia) |
| OTP |
Henri Coandă International Airport (Bucharest, Romania) |
| OSR |
Leoš Janáček Airport Ostrava (Czech Republic) |
| ORD |
O'Hare International Airport (Chicago, USA) |
| OAX |
Oaxaca International Airport (Mexico) |
| OHD |
Ohrid Airport (North Macedonia) |
| OLM |
Olympia Regional Airport (Washington, USA) |
| OMS |
Omsk Tsentralny Airport (Russia) |
| ONS |
Onsite |
| OMR |
Oradea Airport (Romania) |
| ORN |
Oran Es Sénia Airport (Algeria) |
| OSL |
Oslo Gardermoen Airport (Norway) |
| OSL |
Oslo Gardermoen Airport |
| OTP |
Otopeni International Airport (Bucharest) |
| OUA |
Ouagadougou Airport (Burkina Faso) |
| OUA |
Ouagadougou International Airport (Burkina Faso) |
| OUL |
Oulu Airport (Finland) |
| ORY |
Paris Orly Airport (France) |
| OTZ |
Ralph Wien Memorial Airport (Alaska, USA) |
| OVB |
Tolmachevo Airport (Novosibirsk, Russia) |
| OZH |
Zaporizhzhia International Airport (Ukraine) |
| OSD |
Åre Östersund Airport (Sweden) |
| OMA |
Eppley Airfield (Omaha, Nebraska, USA) |
| OGG |
Kahului Airport (Hawaii, USA) |
| OGDP |
Ocean Grove Holiday Park |
| ONTT |
Office National du Tourisme |
| ONTT |
Office national du tourisme tunisien |
| OSFR |
Office of State Federal Relations |
| OAG |
Official Airlines Guide |
| Olta |
Ohel Leah Torah Academy |
| OIT |
Oita Airport (Japan) |
| OKJ |
Okayama Airport (Japan) |
| OLB |
Olbia Costa Smeralda Airport (Italy) |
| OTGC |
On the go changer |
| ONH |
Ongkos Naik Haji |
| OBT |
Online Booking Tool |
| OBTs |
Online Booking Tools |
| OJP |
Online Journey Planner |
| OTA |
Online Travel Agency |
| OBRC |
Ontario Bird Records Committee |
| ONT |
Ontario International Airport (California, USA) |
| OTTA |
Oregon Tour and Travel Alliance |
| OTDC |
Orissa Tourism Development Authority |
| OCTB |
Osaka Convention Tourism Bureau |
| ORTE |
Overall Rural Tourism Experience |
| OKC |
Will Rogers World Airport (Oklahoma City, USA) |