Complex sentence: On May 22,2012, Delta agreed to sublease 88 AirTran Boeing 717 aircraft from Southwest Airlines, which were primarily intended to replace inefficient 50-seat regional jets flown by Delta Connection and some older DC-9s.
Split into simpler sentences: On May 22,2012, Delta agreed to sublease 88 AirTran Boeing 717 aircraft from Southwest Airlines. These used aircraft were primarily intended to replace inefficient 50-seat regional jets flown by Delta Connection and some older DC-9s.