You can use this application to make your travel day even easier. But customers need to log in or register themselves to use this app for check-in. There are some other features also inbuilt with this app so you can check in as a guest. Here you just need to enter your confirmation number this will help you to automatically checked in 24 hours before your flight. But if you are facing any problem to use this application then call Frontier Airlines Reservations Number +1-800-278-1680 and sort out all your queries and concerns.