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. Check-In at the Airport If you’re unable or prefer not to check in online, you can do so at the airport using either self-service kiosks or by visiting a check-in counter. United has made its kiosks easy to use, and they’re available at most major airports. These machines allow you to check in, print boarding passes, pay for baggage, and select or change seats. United check-in counters open approximately 3–4 hours before departure and close 45–60 minutes prior, depending on your destination. For customers needing extra help such as those with group reservations, excess baggage, or complex itineraries—speaking with an agent is often the best option. Airport staff are trained to resolve last-minute booking issues and can rebook or reissue boarding passes in case of missed flights or schedule changes. Mobile Boarding Pass and Bag Drop One of the biggest conveniences of online check-in is that it allows you to use a mobile boarding pass, which can be scanned directly at TSA security and the boarding gate. If you’ve checked in via the app, you’ll receive real-time updates about gate changes, delays, or boarding announcements. United also offers self tagging and baggage drop kiosks, which make checking luggage much faster than waiting in line at a staffed counter. Just remember that if you're dropping off bags, you still need to meet the 45-minute domestic or 60-minute international deadlines. If you miss the cutoff—even by a few minutes—United may deny boarding or rebook your flight, potentially with fees or fare differences involved. Final Thoughts While United Airlines doesn’t require you to check in exactly 24 hours before your flight, it’s strongly encouraged to do so as early as possible within that window. Checking in early ensures that you secure your preferred seat, avoid long airport lines, and receive notifications about your flight. However, the most important detail to remember is that check-in must be completed before the official cutoff times: 45 minutes before domestic flights and 60 minutes before international flights, regardless of whether you checked in online or not. By using United’s user-friendly mobile app [1_866 551 1186 or website, passengers can take control of their travel experience from the comfort of home. But always leave yourself plenty of buffer time especially if checking bags, traveling internationally, or flying from a large or unfamiliar airport. And if anything prevents you from checking in online, airport agents and self-service kiosks are available to assist. In the end, being informed and punctual ensures your trip with United Airlines starts off without a hitch.