Complex sentence: The new Airbus A320neo family has been proposed for short to medium haul, while the Airbus 350, the Boeing 777-300ER, and the Boeing 777X are being considered to expand the long-haul fleet.
Split into simpler sentences: The new Airbus A320neo family has been proposed for short to medium haul. While the Airbus 350 the Boeing 777-300ER and the Boeing 777X are being considered to expand the long-haul fleet.