It can help to know what airlines your carrier partners with, in case you need to be rebooked on another airline. In addition to partnerships like code shares, when an airline operates a flight on behalf of another, or alliances, most airlines also have relationships known as interline agreements that allow them to transfer passengers to flights on other carriers.
This information isn’t always readily available online; experts suggest calling an airline’s customer service for more guidance.
Be aware that if you have a ticket with a low-cost airline, like Frontier Airlines, Southwest Airlines or Spirit Airlines, you are most likely out of luck: They generally do not rebook on any other carrier.
For example, if your United Airlines flight is canceled because of reasons within the carrier’s control, such as understaffing, and you are rerouted to a flight that departs the next day, you are entitled to a voucher for food, a nearby partner hotel and transportation. If a room is not available at the airline’s hotel, and you must find another accommodation, United will reimburse you for “reasonable hotel costs.” There’s nothing on the United customer-service site indicating that food receipts or taxi receipts will be reimbursed.
If a delay or cancellation is the airline’s fault, most major carriers can also rebook you on another airline. A few have this ability regardless of what led to the disruption.
In most instances, American Airlines will rebook you on another airline if there are no American flights until the next day. Delta Air Lines also commits to organizing flights on alternative airlines if necessary, though it is not clear under what circumstances it will do this.