What is the cheapest day to fly on Frontier Airlines? Frontier Airlines fares are typically cheaper on Tuesdays, Wednesdays, and Saturdays, thanks to lower travel demand on these days. On the other hand, Fridays and Sundays are considered peak travel timesFrontier Airlines fares are typically cheaper on Tuesdays, Wednesdays, and Saturdays,thanks to lower travel demand on these days. On the other hand, Fridays and Sundays are considered peak travel times with higher ticket prices.