Complex sentence: The 16 raids on Berlin cost Bomber Command more than 500 aircraft, with their crews killed or captured, which was a loss rate of 5.8%, which was above the 5% threshold that was considered the maximum sustainable operational loss rate by the RAF.
Split into simpler sentences: The 16 raids on Berlin cost Bomber Command more than 500 aircraft, with their crews killed or captured. This was a loss rate of 5.8%, which was above the 5% threshold that was considered the maximum sustainable operational loss rate by the RAF.