Complex sentence: The 727-100 first flew in 1963 and entered service with Eastern Air Lines the following year; the stretched 727-200 flew in 1967 and entered service with Northeast Airlines later that year.
Split into simpler sentences: The 727-100 first flew in 1963 and entered service with Eastern Air Lines the following year. The stretched 727-200 first flew in 1967 and entered service with Northeast Airlines later that year.