| O | ||
| Oaxaca, Mexico (OAX) | Omboue, Gabon (OMB) | Osijek, Croatia (OSI) |
| Obano, Indonesia (OBD) | Omsk, Russia (OMS) | Oskarshamn, Sweden (OSK) |
| Obihiro, Japan (OBO) | Ondangwa, Namibia (OND) | Oslo, Norway (OSL) |
| Ocho Rios, Jamaica (OCJ) | Oradea, Romania (OMR) | Oslo, Norway - Sandefjord (TRF) |
| Odense, Denmark (ZBQ) | Oran, Algeria (ORN) | Ostersund, Sweden (OSD) |
| Odessa, Ukraine (ODS) | Orange, New South Wales, Australia (OAG) | Ostrava, Czech Republic (OSR) |
| Ohrid, Macedonia (OHD) | Oranjemund, Namibia (OMD) | Otu, Colombia (OTU) |
| Oita, Japan (OIT) | Orebro, Sweeden - Obrebro-Bofors (ORB) | Ouagadougou, Burkina Faso (OUA) |
| Okaba, Indonedia (OKQ) | Orenburg, Russia (REN) | Ouargla, Algeria (OGX) |
| Okayama, Japan (OKJ) | Ormara, Pakistan (ORW) | Ouarzazate, Morocco (OZZ) |
| Okhotsk, Russia (OHO) | Ornskoldsvik, Sweden (OER) | Oudomxay, Laos (ODY) |
| Okinawa, Japan (OKA) | Orsk, Russia (OSW) | Oujda, Morocco (OUD) |
| Okoshiri, Japan (OIR) | Orsta-Volda, Norway (HOV) | Oulu, Finland (OUL) |
| Oksibil, Indonesia (OKL) | Osaka, Japan - all airports (OSA) | Ouvea, New Caledonia (UVE) |
| Olbia, Italy (OLB) | Osaka, Japan - Itami (ITM) | Ovda, Israel (VDA) |
| Olpoi, Vanuatu (OLJ) | Osaka, Japan - Kansai Intl (KIX) | Oyem, Gabon (OYE) |
| Olympic Dam, SA, Australia (OLP) | Oshima, Japan (OIM) |