Complex sentence: The RNAS and the RFC (and after April 1918 the RAF) used the type as a trainer after it had been withdrawn from operational service and like the Sopwith Pup, it proved a popular personal aircraft for senior officers.
Split into simpler sentences: The RNAS and the RFC (and after April 1918 the RAF) used the type as a trainer after its combat operational days were over. Like the Pup, it proved a popular personal aircraft for senior officers.