Complex sentence: Orly International Airport was expanded several times during the late 1950s and 1960s and the relationship remained strained, but the Orly Air Base operation continued until March 1967 when it was closed as part of the general American withdrawal from France as part of operation FRELOC.
Split into simpler sentences: Orly International Airport was expanded several times during the late 1950s and 1960s and the relationship remained strained. The Orly Air Base operation continued until March 1967 when it was closed as part of the general American withdrawal from France as part of operation FRELOC.