Frontier Airlines PHX Terminal operating out of Phoenix Sky Harbor International Airport's Terminal 3 is Frontier Airlines (PHX). Offering both domestic and some international flights, Frontier is well-known for its affordable pricing. For convenience, travelers can check in at self-service kiosks or at the airline's designated counters. There are several places to dine and shop in the terminal, so you can wait in comfort before your trip. The entire Terminal 3 has free Wi-Fi for passengers looking for further conveniences. Frontier is a well-liked option for travelers on a tight budget, so be sure to arrive early to beat security and check-in.