Complex sentence: He was also an amateur pilot, but dissatisfied with the amount of real flight training that was available, he decided to build a ground-based device to provide such training without the restrictions of weather and the availability of aircraft and flight instructors.
Split into simpler sentences: He was also an amateur pilot, but was not satisfied with the amount of real flying training that was available. He decided to build a ground-based device to provide such training without the restrictions of weather and the availability of aircraft and flight instructors.