Three-day sales are apparently all the rage this week, the newest entry coming from Frontier Airlines, good for noon Monday-noon Thursday travel through May 20. Fares do require a 14 day advance purchase and all purchases must be made by January 23.
Upgrades from 'Economy' to 'Classic' start at $20, and to 'Classic Plus' for $50.
Beware of the following blackout dates: February 13, 16, March 6-8, March 13 - 15, March 20 - 22, March 27 - 29, April 3 - 5, April 10 - 11, and April 13.
For further details, visit FrontierAirlines.com, and check your city page for fares.