Complex sentence: Delta operates the largest fleets of Boeing 717, Boeing 757, Boeing 767, McDonnell Douglas MD-88, and McDonnell Douglas MD-90 aircraft in the world, and the largest fleet of Airbus A330 aircraft of any US airline.
Split into simpler sentences: Delta operates the largest fleets of Boeing 717, Boeing 757, Boeing 767, McDonnell Douglas MD-88, and McDonnell Douglas MD-90 aircraft in the world. The carrier also operates the largest fleet of Airbus A330 aircraft of any US airline.