Travelers can check in for their flight 24 hours before their departure time online or using the United mobile app, so this is a change that will really only impact passengers attempting to check in at an airport kiosk.
A Complete Guide
When preparing for a flight with United Airlines, understanding the airline’s check in process is essential for a smooth travel experience. One of the most frequently asked questions among travelers is: Does United require check in exactly 24 hours before the flight? The short answer is no United Airlines does not require you to check in exactly 24 hours prior to departure, but it does allow you to begin checking in at that time. Online and mobile check in opens exactly 24 hours before the scheduled departure time of your flight and remains available until the check in cutoff period, which depends on whether your flight is domestic or international. Knowing how this process works, including when check in closes, is key to avoiding missed flights or unexpected surprises at the airport.[1_866 551 1186
24 Hour Online Check In Window
United Airlines offers online check in through its website and mobile app, opening 24 hours before your flight. This is designed to give passengers enough time to complete necessary tasks ahead of departure, such as confirming flight details, selecting or upgrading seats, adding baggage, updating passport information (for international travel), and accessing a digital boarding pass. This flexibility is particularly convenient for travelers who want to skip airport lines and head straight to security or baggage drop.
To complete the online check in, simply visit United’s website or open the United app, click “Check in,” and enter your confirmation number and last name. From there, you can follow the on screen steps to complete the check in process. Once complete, you’ll be issued a mobile or printable boarding pass. If you have no bags to check, you can proceed directly to TSA screening. If you do have checked baggage, you can drop it off at United’s self service kiosks or baggage counters at the airport.
It’s important to note that while United offers check in starting 24 hours before your flight, you’re not required to check in exactly at that time. The 24 hour mark simply marks the earliest point at which check in becomes available. However, waiting too long especially within an hour of departure can be risky, as you may miss important deadlines depending on your flight type and airport.
Check In Deadlines: Domestic vs. International Flights
United Airlines has strict check in deadlines that all passengers must meet, regardless of whether they checked in online, at a kiosk, or at the counter. For domestic flights, passengers must check in and have any checked baggage accepted no later than 45 minutes before scheduled departure. For international flights, the check in and baggage drop deadline is 60 minutes before departure. These cut off times are strictly enforced to ensure on time boarding and departures.
Until recently, United had allowed check in as late as 30 minutes before takeoff for domestic passengers without checked baggage. However, as of June 3, 2025, that grace period has been eliminated. Now, all domestic passengers, regardless of whether they have checked bags, must be checked in by 45 minutes prior to departure. This means that even if you don’t need to drop bags, the airline will not let you board if you haven’t checked in by that time.
It’s also worth noting that boarding typically begins 30–40 minutes before departure, and gates close 15 minutes prior to takeoff. So, simply arriving at the airport or completing check in just in time for the cutoff doesn’t guarantee you’ll make the flight. United recommends arriving at least 2 hours early for domestic flights and 3 hours early for international travel to allow time for security screening, unexpected delays, and getting to your departure gate.
Exceptions to Online Check In
While most passengers are eligible for online or mobile check in, there are exceptions. In certain situations, United may require travelers to check in at the airport instead:
Unaccompanied Minors – Children traveling alone often require special handling and documentation, which must be completed in person.
Special Assistance Requests – Travelers who need wheelchair assistance, traveling with service animals, or with medical equipment must typically check in at the counter.
Passport or Visa Issues If you're traveling internationally and your passport or visa needs to be verified, United may require you to check in at the counter.
Flight Irregularities – If there are schedule changes, ticketing issues, or delays, online check in might be unavailable, and you’ll be directed to an agent at the airport.
Codeshare Flights – If you’re flying on a codeshare flight operated by a different airline (e.g., Lufthansa, Air Canada), check in may need to be completed through the partner airline's system.