Oakland Airmotive Super V - N617B, N617B, N617B - (see also Bay Aviation and Pine Air)
Oberlerchner
     JOB 15-150/2 - D-EJHO
     Mg 19a Steinadler - BGA 2903
O'Dell Son of Beech - N67J
Ogden
     Osprey PB - X150W
     Osprey PC - X187N
Oldfield
     Baby Great Lakes - N22872 - N26W - N6754, N6754
     Baby Lakes - C-FBKY
     Oldfield Special - N9Y
OMAC (Old Man's Aircraft Company)
     Laser 300 - N301L
Omega BS-12 - N267B
Omni Weld Questor - N701W
ONERA Deltaviex - F-WBHA, F-WBHA
On Mark
     A-26A Counter-Invader - N99218
     YB-26K - USAF: 64-17645
     B-26K Counter Invader - USAF: 44-35634, 44-35634, 64-17640, 64-17653
     Marketeer - N202R - N40Y - N500M - N501N
     Marksman - N256H
     Marksman C - ZS-CVD
Option Air Acapella 200-S - N360CB, N360CB - N455CB
Ordnance Engineering Company - (see Orenco)
Orenco
     B - USASC: 33765
     D - USAAS: photo
     D2 PW-3 - USAAS: 64142, 64144
     F-4 Tourister - N2145
Orta Saint-Hubert G1 - OO-ABI - OO-AKY - OO-AMS
Oskbes-MAI - (see MAI)
Oškinis
     BrO-1M - photo
     BrO-18 Boruzé - photo
     BrO-20 Pukelis - photo
     BrO-21 Vyturys - photo
Osprey
     GP3 Osprey 2 - N3GP
     GP-4 - N247MW
Ott Hessenland - photo
Otto C.I - German AAS: photo
Ouest CAO-200 - photo