What is Frontier Check In? It's the quick and convenient way to check in for your flight with Frontier Airlines. With easy-to-use online tools, you can save time and effort while ensuring your journey goes as smoothly as possible. But just what do you need to know before checking in? In this ultimate guide to Frontier Check In, we'll be covering everything you need to know about how the process works, when and where to check in, and what documents may be required for your particular flight. By the end of this guide, you'll have a complete overview of the check-in process with Frontier Airlines.