In Europe (and early in Southwest's history) luggage is not transferred from one flight to another, even if both flights are with the same airline. This saves costs and is thought to encourage passengers to take direct flights. Tickets are not sold with transfers, so the airline can avoid responsibility for passengers' connections in the event of a delay. Low-cost carriers often have a sparse schedule with one flight per day and route, so it would be hard to find an alternative for a missed connection. Modern US-based low-cost carriers generally transfer baggage for continuing flights, as well as transferring baggage to other airlines. Many airlines opt to have passengers board via stairs, since jetways generally cost more to lease.