Frontier encourages all passengers to check in online or via its mobile app up to 24 hours in advance. Doing this not only helps you skip lines at the airport but can also save you significant money on baggage fees. At the airport, options include: Self-service kiosks to print boarding passes and bag tags Customer service counters for special assistance, such as oversized bag... https://airportsterminalhub.com/airlines/frontier-airlines/frontier-airlines-denver-international-airport-den-terminal/