The document that proves that the check-in passed successfully and the person is allowed to enter the airplane is a boarding plane. It must be released to each passenger prior to the flight.

Boarding passes are issued upon check-in.

If online check-in is available, you will be able to get your boarding pass before going to the airport. Don't forget to print your boarding pass! (Even if your carrier supports paperless boarding passes, the departure airport may or may not have the proper equipment to process them.) If online check-in is not available, bring a printout of your e-ticket to the airport to receive your boarding pass prior to your departure.