 The XPW-9 competed with the Curtiss Model 33 for contracts for a pursuit aircraft to replace the Thomas-Morse MB-3A in the United States Army Air Service.Ultimately, both models were accepted; the Curtiss aircraft was designated PW-8 and the Model 15 PW-9.The Air Service preferred the PW-9, which outperformed the PW-8 in all performance aspects except speed, and was built on a more rugged and easier to maintain design, ordering 113 aircraft (only 25 PW-8s were procured).