While the U.S. Army had not found the Model 269 adequate for combat missions, in 1964 it adopted the Model 269A as its training helicopter to replace the TH-23 and designated it the TH-55A Osage. 792 TH-55 helicopters would be delivered by 1969, and it would remain in service as the U.S. Army's primary helicopter trainer until it was replaced in 1988 by the UH-1 Huey. At the time of its replacement, over 60,000 U.S. Army pilots had trained on TH-55 making it the U.S. Army's longest serving training helicopter. In addition to the U.S. Army, Hughes delivered TH-55/269/300s to other military customers.