O - Observation Aircraft

Model	Designation	Manufacturer	Engine(s)	Crew	Other
XO-1	Falcon	Curtiss	1 Liberty or 1 Packard 1A-1500	2
O-1	Falcon	Curtiss	1 Curtiss V-1150	2
O-1A	Falcon	Curtiss	1 Liberty V-1650-3	2
O-1B	Falcon	Curtiss	1 Curtiss V-1150-5	2
O-1C	Falcon	Curtiss	1 Curtiss V-1150-5	2
Y1O-1E	Falcon	Curtiss	1 Curtiss V-1150-5	2	XBT-4
O-1E	Falcon	Curtiss	1 Curtiss V-1150-5	2
O-1F	Falcon	Curtiss	1 Curtiss V-1150-5	2
XO-1G	Falcon	Curtiss	1 Curtiss V-1150	2
Y1O-1G	Falcon	Curtiss	1 Curtiss V-1150	2
O-1G	Falcon	Curtiss	1 Curtiss V-1150	2
XO-2		Douglas	1 Liberty V-1650 or 1 Packard 1A-1500
O-2		Douglas	1 Liberty V-1650
O-2A		Douglas	1 Liberty V-1650
O-2B		Douglas	1 Liberty V-1650
O-2C		Douglas	1 Liberty V-1650
O-2D		Douglas	1 Liberty V-1650
O-2E		Douglas	1 Liberty V-1650
O-2F		Douglas	1 Liberty V-1650		cancelled
O-2G		Douglas	1 Liberty V-1650		cancelled
O-2H		Douglas	1 Liberty V-1650A
O-2J		Douglas	1 Liberty V-1650
O-2K		Douglas	1 Liberty V-1650
O-2M		Douglas	1 Liberty V-1650
XO-3	Mohawk	Dayton-Wright	1 Wright V-1950		cancelled
XO-4		Martin	1 Liberty V-1650		cancelled
O-5		Douglas	1 Liberty V-1650	2
XO-6		Thomas-Morse	1 Liberty V-1650
O-6		Thomas-Morse	1 Liberty V-1650
XO-6B		Thomas-Morse	1 Pratt & Whitney R-1340 Wasp
O-7		Douglas	1 Packard 1A-1500
O-8		Douglas	1 Curtiss R-1454
O-9		Douglas	1 Packard 1A-1500
XO-10		Loening	1 Wright V-1460	2	XOA-1A
XO-11	Falcon	Curtiss	1 Liberty V-1650	2
O-11	Falcon	Curtiss	1 Liberty V-1650	2
O-11A	Falcon	Curtiss	1 Liberty V-1650	2
O-12	Falcon	Curtiss	1 Pratt & Whitney R-1340 Wasp	2
XO-13	Falcon	Curtiss	1 Curtiss V-1570 Conqueror	2
XO-13A	Falcon	Curtiss	1 Curtiss V-1570 Conqueror	2
O-13B	Falcon	Curtiss	1 Curtiss V-1570 Conqueror	2
YO-13C	Falcon	Curtiss	1 Curtiss V-1570 Conqueror	2
YO-13D	Falcon	Curtiss	1 Curtiss V-1570 Conqueror	2
XO-14		Douglas	1 Wright R-790 Whirlwind
XO-15		Keystone	1 Wright R-790 Whirlwind
XO-16	Falcon	Curtiss	1 Liberty V-1650	2
XO-17	Courier	Consolidated	1 Wright R-790-1 Whirlwind		PT-3
XO-17A	Courier	Consolidated	1 Wright R-790 Whirlwind	2	XPT-8
XO-18	Falcon	Curtiss	1 Curtiss H-1640 Chieftain	2
XO-19		Thomas-Morse	1 Pratt & Whitney R-1340 Wasp	2
O-19		Thomas-Morse	1 Pratt & Whitney R-1340 Wasp	2
O-19A		Thomas-Morse	1 Pratt & Whitney R-1340 Wasp	2
O-19B		Thomas-Morse	1 Pratt & Whitney R-1340 Wasp	2
O-19C		Thomas-Morse	1 Pratt & Whitney R-1340 Wasp	2
O-19D		Thomas-Morse	1 Pratt & Whitney R-1340 Wasp	2
O-19E		Thomas-Morse	1 Pratt & Whitney R-1340-15 Wasp	2
YO-20		Thomas-Morse	1 Pratt & Whitney R-1690 Hornet	2
XO-21		Thomas-Morse	1 Curtiss H-1640 Chieftain	2
XO-21A		Thomas-Morse	1 Curtiss V-1570 Conqueror	2
YO-22		Douglas	1 Pratt & Whitney R-1340 Wasp
O-22		Douglas	1 Pratt & Whitney R-1340 Wasp
YO-23		Thomas-Morse	1 Curtiss V-1570 Conqueror	2
O-24		Curtiss	1 Pratt & Whitney R-1340 Wasp		cancelled
O-25		Douglas	1 Curtiss V-1570 Conqueror	2
XO-25A		Douglas	1 Curtiss V-1570 Conqueror	2
O-25A		Douglas	1 Curtiss V-1570 Conqueror	2
O-25B		Douglas	1 Curtiss V-1570 Conqueror	2
O-25C		Douglas	1 Curtiss V-1570 Conqueror	2
Y1O-26		Curtiss	1 Curtiss V-1570A Conqueror	2
XO-27		Fokker	2 Curtiss V-1570-23 Conqueror	3	XB-8
Y1O-27		Fokker	2 Curtiss V-1570-29 Conqueror	3	YB-8
XO-27A		Fokker	2 Curtiss V-1570-23 Conqueror	3
O-28	Corsair	Vought	1 Pratt & Whitney R-1340 Wasp	2	O2U-3
O-29		Douglas	1 Wright V-1750 Cyclone	2
Y1O-29A		Douglas	1 Wright V-1750 Cyclone	2
O-29A		Douglas	1 Wright V-1750 Cyclone	2
O-30		Curtiss	1 Curtiss V-1570 Conqueror		cancelled
XO-31		Douglas	1 Curtiss V-1570-25 Conqueror	2
YO-31		Douglas	1 Curtiss V-1570 Conqueror	2
Y1O-31A		Douglas	1 Curtiss V-1570 Conqueror	2	Y1O-43
O-31A		Douglas	1 Curtiss V-1570 Conqueror	2
YO-31B		Douglas	1 Curtiss V-1570 Conqueror
YO-31C		Douglas	1 Curtiss V-1570 Conqueror	2
Y1O-31C		Douglas	1 Curtiss V-1570 Conqueror	2
O-32		Douglas	1 Pratt & Whitney R-1340-3 Wasp
O-32A		Douglas	1 Pratt & Whitney R-1340-3 Wasp		BT-2A
Y1O-33		Thomas-Morse	1 Curtiss V-1570 Conqueror	2
O-34		Douglas	1 Curtiss V-1570 Conqueror
XO-35		Douglas	2 Curtiss V-1570 Conqueror
Y1O-35		Douglas	2 Curtiss V-1570-27 Conqueror		O-35
O-35		Douglas	2 Curtiss V-1570-27 Conqueror		Y1O-35
XO-36		Douglas	2 Curtiss V-1570-23 Conqueror		XB-7
O-37		Keystone	1 Pratt & Whitney R-1340 Wasp		cancelled
O-38		Douglas	1 Pratt & Whitney R-1690-3 Hornet
O-38A		Douglas	1 Pratt & Whitney R-1690-5 Hornet
O-38B		Douglas	1 Pratt & Whitney R-1690-5 Hornet
O-38C		Douglas	1 Pratt & Whitney R-1690-5 Hornet
O-38D		Douglas	1 Wright R-1820 Cyclone
O-38E		Douglas	1 Pratt & Whitney R-1690-5 Hornet
O-38F		Douglas	1 Pratt & Whitney R-1690-5 Hornet
O-39	Falcon	Curtiss	1 Curtiss V-1570 Conqueror	2
YO-40		Curtiss	1 Wright R-1820 Cyclone
YO-40A		Curtiss	1 Wright R-1820 Cyclone
Y1O-40B	Raven	Curtiss	1 Wright R-1820 Cyclone		O-40B
O-40B	Raven	Curtiss	1 Wright R-1820 Cyclone		Y1O-40B
Y1O-41		Thomas-Morse	1 Curtiss V-1570 Conqueror	2
O-42		Thomas-Morse			cancelled
Y1O-43		Douglas	1 Curtiss V-1570-59 Conqueror	2	Y1O-31A
O-43A		Douglas	1 Curtiss V-1570-59 Conqueror	2
O-44		Douglas	2 Wright R-1820-45 Cyclone	5	B-11, YOA-5
O-45		Martin	2 Wright R-1820-17 Cyclone		B-10
XO-46A		Douglas	1 Pratt & Whitney R-1535-7 Twin Wasp Junior	2
O-46A		Douglas	1 Pratt & Whitney R-1535-7 Twin Wasp Junior	2
XO-47		North American	1 Wright R-1820-49 Cyclone	3
O-47A		North American	1 Wright R-1820-49 Cyclone	2
O-47B		North American	1 Wright R-1820-57 Cyclone	2
XO-48		Douglas	1 Wright R-1670-3	2	cancelled
O-49	Vigilant	Stinson	1 Lycoming R-680-9	2	L-1
O-49A	Vigilant	Stinson	1 Lycoming R-680-9	2	L-1A
O-49B	Vigilant	Stinson	1 Lycoming R-680-9	2	L-1B
YO-50		Bellanca	1 Ranger V-770	2
YO-51	Dragonfly	Ryan	1 Pratt & Whitney R-985-21 Wasp Junior	2
O-52	Owl	Curtiss	1 Pratt & Whitney R-1340 Wasp	2
O-53	Havoc	Douglas	2 Wright R-2600 Cyclone		A-20B, cancelled
YO-54		Stinson	1 Continental O-170	3
YO-55		Erco	1 Continental O-170
O-56	Ventura	Lockheed	2 Wright R-2600-13 Cyclone		B-34B, B-37
YO-57	Grasshopper	Taylorcraft	1 Continental O-170-3		L-2
O-57	Grasshopper	Taylorcraft	1 Continental O-170-3		L-2
O-57A	Grasshopper	Taylorcraft	1 Continental O-170-3		L-2A
YO-58	Grasshopper	Aeronca	1 Continental O-170-3	2	L-3
O-58	Grasshopper	Aeronca	1 Continental O-170-3	2	L-3
O-58A	Grasshopper	Aeronca	1 Lycoming O-145	2	L-3A
O-58B	Grasshopper	Aeronca	1 Continental O-170-3	2	L-3B
YO-59	Grasshopper	Piper	1 Continental O-170-3		L-4
O-59	Grasshopper	Piper	1 Continental O-170-3		L-4
O-59A	Grasshopper	Piper	1 Continental O-170		L-4A
XO-60		Kellett	1 Jacobs R-775	1
YO-60		Kellett	1 Jacobs R-915-3	1
YO-61		Pitcairn	1 Jacobs R-915		cancelled
O-62	Sentinel	Stinson	1 Lycoming O-435-1		L-5
XO-63	Grasshopper	Interstate	1 Franklin O-200	2	XL-6

O-1A	Bird Dog	Cessna	1 Continental O-470-11	1	L-19A, OE-1A
TO-1A	Bird Dog	Cessna	1 Continental O-470-11	2
O-1B	Bird Dog	Cessna	1 Continental O-470-11	1	OE-1
O-1C	Bird Dog	Cessna	1 Continental O-470-2	1	OE-2
O-1D	Bird Dog	Cessna	1 Continental O-470-15	1	L-19D
TO-1D	Bird Dog	Cessna	1 Continental O-470-15	2	TL-19D
O-1E	Bird Dog	Cessna	1 Continental O-470-11	1	L-19E
O-1F	Bird Dog	Cessna	1 Continental O-470-15	1
O-1G	Bird Dog	Cessna	1 Continental O-470-11	1
O-2A	Skymaster	Cessna	2 Continental O-360
O-2B	Skymaster	Cessna	2 Continental O-360
YO-3A		Lockheed	1 Continental O-360	2
ZO-4A					cancelled
O-5A		DeHavilland Canada	4 Pratt & Whitney PT106
EO-5B		DeHavilland Canada	4 Pratt & Whitney PT106
EO-5C		DeHavilland Canada	4 Pratt & Whitney PT6A-50
TO-5C		DeHavilland Canada	4 Pratt & Whitney PT6A-50