United Airlines is changing its check-in policy. Starting June 3, all U.S. passengers must check in at least 45 minutes before takeoff — or risk losing their seat.

United Airlines is making a change to its check-in time policy. United customers must check in for a domestic flight at least 45 minutes before a flight without any checked bags starting June 3. The prior policy required travelers to check in at least a half hour before a flight.