For international flights you must present a passport that is valid at least 180 days after your return.

For domestic flights you must present a valid government issued photo ID.

Additionally, you must present a valid paper ticket when electronic tickets are not applicable.

Electronic ticket receipts are not required at the time of check-in. Boarding passes are issued at the time of check-in based on your identification and matching reservation information that is stored in the airline’s reservation system.

If using electronic tickets we suggest that you bring a copy of your flight itinerary to the airport. You may be asked to show your flight itinerary to airport security personnel while standing in the check-in line.

IMPORTANT NOTE: Make sure that you have valid visas and transit visas for international travel. Visas may be required by all foreign countries visited on your trip, including at all transit airports. U.S. passport holders can check visa requirements at: http://travel.state.gov/travel/tips/brochures/brochures_1229.html