A boarding pass is an essential document issued by an airline that allows a passenger to enter the aircraft. It contains important information such as the passenger's name, flight number, departure and arrival times, and the boarding gate. The boarding pass can be printed or stored digitally on a mobile device. Passengers must present their boarding pass at various checkpoints, including security and the boarding gate. It serves as proof that they have completed the check-in process and are authorized to board the flight. Without a valid boarding pass, a passenger cannot access the aircraft.