Say it ain't so, JetBlue! 

In order to appease investors, JetBlue announced Wednesday that it will begin charging for checked bags for its lowest priced tickets.

Beginning in the first half of 2015, the airline said it will create three ticket classes, and only the top two include at least one free checked bag, along with other benefits, including additional TrueBlue points.

Up until now, JetBlue and Southwest were the only two major U.S. airlines that offered a free checked bag.

"This new merchandising platform will enable JetBlue to tailor its offering to individual customers' needs in a way that is simple and transparent," the airline said in a release.

Executives wouldn't give prices for the bag fees, but said it would fluctuate with demand. 

In addition, JetBlue will also add 15 seats to its Airbus A320 planes, increasing capacity to 165 from 150, and reduce average legroom to 33 inches between rows from more than 34 inches. The retrofit of cabins will start in late 2016.

The move is bound to anger loyal customers who enjoyed the legroom and absence of additional fees.

The new pricing structure sounds similar to Frontier's model, which offers its lowest fares if you pay for a checked and/or a carryon bag. American has a similar model with its "choice" fares.

The real question is: Will JetBlue's no-checked-bag fares be the same or lower as their current lowest fares. 

Our guess is they'll be the same, meaning you won't get a "discount" for not checking a bag. J

etBlue reckons they'll earn an extra $400 million per year with these new fare bundles. 

And another question: Will online travel agencies be able to show the different fare bundles? 

Most likely not, so that will drive traffic to JetBlue's website, which is the holy grail for any airline hoping to avoid referral fees from Kayak and the like.

What we do know is that these moves come as JetBlue has been under pressure from investors to boost revenue.

George Hobica is a syndicated travel journalist and founder of the low-airfare listing site Airfarewatchdog.com.