United cabin crew are in line for significant increases in hourly pay under a tentative five-year agreement that includes half-pay during boarding.

Starting Tuesday, travelers who fail to follow the new policy could be denied the option to check their bags or be forced to miss their flight.

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.