Complex sentence: The chief modifications to the aircraft were a station for the drogue operator and a winch (usually air-driven) to reel in the cable prior to landing; the drogue would often be jettisoned at some location convenient for recovery prior to the aircraft's landing.
Split into simpler sentences: The chief modifications to the aircraft were a station for the drogue operator and a winch to reel in the cable prior to landing. The drogue would often be jettisoned at some location convenient for recovery prior to the aircraft's landing.