A one-way trip means the customer is booking a flight from one location to another without returning. A round trip, on the other hand, involves booking a flight from one location to another and then back again. An empty-leg flight happens when an aircraft is chartered for a round-trip but flies one leg without passengers. This occurs when the aircraft must return to its base or go elsewhere to serve other customers. Booking an empty-leg trip can save you money through discounted prices compared to one-way or round trips.