Martin XO-4

The Martin XO-4 (Model 71) was a proposed observation aircraft designed by the Glenn L. Martin Company.^[1][2] It was designed to compete with the Curtiss XO-1, Douglas XO-2, and Dayton-Wright XO-3, and was to be powered by a Wright T-3 Tornado or a Liberty V-1650.^[3][4] Although it failed to receive a contract from the United States Navy, a single prototype (allocated the serial number 23-1255) was ordered by the United States Army Air Service, but this contract was canceled before the prototype could be built.^[3][5]

XO-4
General information
Type	Observation
National origin	United States
Manufacturer	Glenn L. Martin Company
Status	Canceled
Number built	0

References

1. "Martin Aircraft Model Designations, Built and Unbuilt" (PDF). Glenn L. Martin Maryland Aviation Museum. Archived from the original (PDF) on May 17, 2008.
2. Duell, Sloan and Pearce (1947). The Official Pictorial History of the AAF. United States Army Air Forces Historical Office.
3. Air Service Information Circular. Director of Air Service. 1923.
4. "O - Observation Aircraft". 2007-03-16. Archived from the original on 2007-03-16. Retrieved 2020-06-15.
5. "USAF Serial Number Search Results". cgibin.rcn.com. Retrieved 2020-06-15.