Frontier Airlines will begin charging up to $100 for a carry-on bag and $2 for coffee or soda. Yes, really. $100 for a carry-on.

This only applies to bags that need to go in the overhead bin, so bags that fit underneath the seat will still be free. The fee will be $25 if paid in advance, and $100 only if passengers wait until they are at the gate to pay or their bags do not fit underneath the seat in front and therefore must go in the overhead compartment.

And if passengers fork over the $2 for a soda, they get to keep the whole can, instead of being served the soda in a dinky cup pre-filled to the brim with ice.

Still...not cool, Frontier.

Most airlines have been charging for checked bags, starting in about 2008. In response, passengers have been carrying more and more on board planes, stuffing suitcases barely within the limit as full as possible, then cramming them into the overhead bins. These fees are one way to get passengers to bring less into the cabins of planes.

And make the airline a pretty penny doing so.

Kate O'Malley, Frontier spokeswoman, said "We don't want to charge that" and that the $100 fee is to get travelers to pay in advance.  She says it's not about increasing corporate profits. Rather, ""it's about Frontier's most loyal customers making it very clear that finding overhead bin space has become increasingly difficult."

Apparently, only disloyal customers bring too much on board, then need to find space in the overhead bin for their bags. The loyal ones just need overhead bin space for...oh, wait, their bags.

Deep-discount carrier Spirit Airlines Inc. started the first carry-on fee three years ago. Allegiant Air, a similar budget carrier, followed.  Airline consultant Jay Sorensen estimated in a December 2011 report that Spirit's carry-on fee brings in $50 million a year. Fees are how Spirit makes most of their overhead, because the ticket prices themselves are too low to garner a large profit margin. 

The fee will start in summer, but a date hasn't been set. O'Malley said that passengers who buy their tickets directly via the Spirit website rather than third-party websites won't have to pay, and that website and check-in procedures will be changed to ensure passengers are aware of potential fees before they get stuck with them at the gate.