United Airlines requires passengers to check in at least 45 minutes before domestic flights and 60 minutes before international flights. This applies whether or not you have checked baggage. Check-in is available online or via the United app starting 24 hours before departure and closes at the cutoff time for your flight type. Failure to check in by the deadline may result in denied boarding.

At the airport, self-service kiosks and ticket counters typically open 3 hours before departure. Curbside check-in, available at most U.S. airports, usually operates from 4 hours to 45 minutes before departure. Baggage must be dropped off before the check-in deadline.

United recommends arriving at the airport 2 hours before domestic flights and 3 hours before international flights to allow enough time for check-in, baggage drop, security screening, and reaching the gate. Boarding typically begins 30–40 minutes before departure, and gates close 15 minutes before domestic flights and 30 minutes before international flights.

Passengers should check in as early as possible within the 24-hour window to select seats, confirm flight details, and avoid last-minute issues. Online and app check-in options allow passengers to skip lines at the airport and proceed directly to security if traveling without checked bags.

In summary:

• Online/App Check-in: Opens 24 hours before, closes 45 min (domestic), 60 min (international)

• Baggage Drop Deadline: Same as check-in cutoff

• Airport Arrival: 2 hrs (domestic), 3 hrs (international)

• Gate Closure: 15 min (domestic), 30 min (international)

Call +1-866-551-1186 for help with check-in or booking.