Airline check-in is the first step for you to board a flight. This step includes verifying your reservation and documents and issuing your boarding pass. There are two ways to use Frontier check-in - ONLINE AND AIRPORT.

https://getairlineshelpdesk.com/check-in/frontier-airlines-check-in

What is the cost of changing a flight on Jetblue? $25 to $75. Maybe, you are right. Jetblue flight change policy is simple and flexible like Jetblue flight tickets fare rules.

https://getairlineshelpdesk.com/flight-change/jetblue-flight-change-policy