- Oakes Municipal AirportIdent: K2D5Serves: Oakes
- Oakesdale AirportIdent: 75DCServes: Oakesdale
- Oakhill AirparkIdent: SC82Serves: Williamson
- Oakland Southwest AirportIdent: KY47Serves: New Hudson
- Oakland Troy AirportIdent: KVLLServes: Troy
- Oakleaf AirportIdent: 9SD8Serves: Hartford
- Oakley AirportIdent: TN79Serves: Nashville
- Oakley Municipal AirportIdent: 1U6Serves: Oakley
- Oakley Municipal AirportIdent: KOELServes: Oakley
- Oakridge Ranch AirportIdent: 26OGServes: Eagle Point
- Oakridge State AirportIdent: K5S0Serves: Oakridge
- Oaks AirportIdent: TX24Serves: Arp
- Oasis Ranger Station - US Government AirportIdent: 9FL7Serves: Everglades City
- Obannon Creek AerodromeIdent: OH66Serves: Goshen
- Oberlander AirportIdent: PA52Serves: Union City
- Oberlin Municipal AirportIdent: KOINServes: Oberlin
- Obi One AirportIdent: 7OH3Serves: Delaware
- Ocala International Airport - Jim Taylor FieldIdent: KOCFServes: Ocala
- Ocean City Municipal AirportIdent: 26NServes: Ocean City
- Ocean County AirportIdent: KMJXServes: Toms River
- Ocean Ridge AirportIdent: E55Serves: Gualala
- Ocean Springs AirportIdent: K5R2Serves: Ocean Springs
- Oceana County AirportIdent: KC04Serves: Hart/Shelby
- Oceano County AirportIdent: L52Serves: Oceano
- Ochoa FieldIdent: 6WA4Serves: Othello
- Ochs Private AirportIdent: 72ORServes: Madras
- Ockel Farms AirportIdent: DE23Serves: Milton
- Oconee County Regional AirportIdent: KCEUServes: Clemson
- Oconomowoc AirportIdent: 0WI8Serves: Oconomowoc
- Ocotillo AirportIdent: L90Serves: Ocotillo Wells
- Ocracoke Island AirportIdent: KW95Serves: Ocracoke
- Odegaard AirportIdent: 57NDServes: Kindred
- Odell Williamson Municipal AirportIdent: K60JServes: Ocean Isle Beach
- Odessa Municipal AirportIdent: K43DServes: Odessa
- Odessa Schlemeyer FieldIdent: KODOServes: Odessa
- Odom's Flying Service AirportIdent: 50FLServes: Jay
- Odom's Roost AirportIdent: 76OKServes: Newcastle
- Oelwein Municipal AirportIdent: KOLZServes: Oelwein
- Offutt Acres AirportIdent: PN02Serves: East Brady
- Ogallala Municipal Airport Searle FieldIdent: KOGAServes: Ogallala
- Ogle County AirportIdent: C55Serves: Mount Morris
- Oglesby Farms Inc. AirportIdent: MS86Serves: Glen Allan
- Ohio County AirportIdent: K7K4Serves: Hartford
- Ohio University AirportIdent: KUNIServes: Albany
- Ohkay Owingeh AirportIdent: KE14Serves: Espanola
- Ohman Ranch AirportIdent: WY12Serves: Gillette
- Ojibwa AirparkIdent: KD11Serves: Weidman
- Okanogan Legion AirportIdent: S35Serves: Okanogan
- Okeechobee County AirportIdent: KOBEServes: Okeechobee
- Okeelanta AirportIdent: FL41Serves: South Bay
- Okmulgee Regional AirportIdent: KOKMServes: Okmulgee
- Okolona Municipal Airport Richard Stovall FieldIdent: K5A4Serves: Okolona
- Oktibbeha AirportIdent: KM51Serves: Starkville
- Olafson Brothers AirportIdent: 03NDServes: Edinburg
- Olcott-Newfane AirportIdent: D80Serves: Burt
- Old 66 StripIdent: 70OKServes: Miami
- Old AerodromeIdent: 9CL7Serves: Browns Valley
- Old Boston AirportIdent: US-1110Serves: Williamsburg
- Old Bridge AirportIdent: K3N6Serves: Old Bridge
- Old Dairy AirportIdent: 3WN2Serves: Washburn