Complex sentence: The Air Force liked the T-37A, but considered it to be underpowered; consequently they ordered an improved version, the T-37B, with uprated J-69-T-25 engines.
Split into simpler sentences: The Air Force liked the T-37A, but felt it was underpowered. As a result, the service ordered an improved version, the T-37B, with uprated J-69-T-25 engines.