+1-844-414-9223 United Check-in is available starting 24 hours before your scheduled departure. Your departure airport and destination may have different requirements for check-in, baggage check, and boarding times. Details can be found on our page describing check-in and airport processing times. If you want to learn more about the check-in process, you can visit TheAirlinesInfo's official website or call their customer service team, which is available 24 hours a day, seven days a week.