Frontier Airlines offers passengers convenient options for check-in. Online Frontier check-in opens 24 hours before departure and allows travellers to select their seats and receive a mobile or printable boarding pass. Airport check-in is also available at Frontier's ticket counters or kiosks, where you can obtain your boarding pass. Passengers should arrive early to ensure a smooth check-in process and allow enough time for security checks. Frontier Airlines recommends that passengers check in at least 2 hours before departure to ensure a hassle-free travel experience.