Complex sentence: Often these airlines offer no refunds or transfers to later flights in the event of missed flights; if the aircraft leaves on time without a passenger who arrived late from a connecting flight, the passenger will have to buy a wholly new ticket for the next flight.
Split into simpler sentences: Often these airlines offer no refunds or transfers to later flights in the event of missed flights. If the aircraft leaves on time without a passenger who arrived late from a connecting flight, the passenger must buy a new ticket for the next flight.