Complex sentence: Before the revolution, the U.S. and Libya had already reached agreement on U.S. withdrawal from Wheelus; this proceeded according to plan, and the facility was turned over to the new Libyan authorities on June 11,1970.
Split into simpler sentences: Before the revolution, the US and Libya had already reached agreement on US withdrawal from Wheelus. This proceeded according to plan, and the facility was turned over to the new Libyan authorities on June 11,1970.