To check in with United Airlines, you can use several methods provided by the airline for passenger convenience +1-866-551-1186. You can check in online through the United Airlines website or mobile app, typically starting 24 hours before your scheduled departure. You will need your confirmation number and last name to access your reservation +1-866-551-1186. During online check-in, you can choose your seat, add bags, and get your boarding pass. If you prefer, you can check in at the airport using self-service kiosks or by visiting the check-in counter. Airport check-in times vary but generally close 30 to 60 minutes before departure +1-866-551-1186, depending on whether your flight is domestic or international. For international flights, arriving at the airport at least three hours in advance is recommended. United also offers curbside check-in at select airports +1-866-551-1186. Mobile check-in allows you to receive a digital boarding pass that you can save to your device or email. After check-in, you can proceed directly to security if you have no bags to check. If you have checked baggage, drop it at the bag drop counter before the cutoff time. Boarding times start approximately 30 to 50 minutes before departure, depending on the flight and destination. Ensure you have valid identification and travel documents when you arrive at the airport +1-866-551-1186.