Complex sentence: The JATO JUNIOR Was an attempt by Aerojet Engineering to introduce smaller JATO unit to small commercial aircraft, but was blocked by the U.S. Navy Bureau of Aeronautics.
Split into simpler sentences: The JATO JUNIOR was an attempt by Aerojet Engineering to introduce smaller JATO unit to small commercial aircraft. The attempt was blocked by the U.S. Navy Bureau of Aeronautics.