First, the flight was on time and the crew was very friendly and efficient. The business model, as is increasingly the case, is to charge for everything (bag, carryon, seat assignment, etc.) I booked through expedia and didn't notice this....my bad. All of this would be tolerable, but the line to check a bag was enormous in Denver and had to wait almost 30 minutes...ouch. Also, since I booked via expedia, I could not check in online...had to call multiple times to get reaolved. Very frustrating....seems like this shouldn't be an edge case to accommodate 3rd party apps for check in...Couldn't even do it on their website. Book with Frontier vs. 3P app to save hassle until fixed.