I apologize for sending us down the Aspire road. I'm almost certain that the original item on the YX page mentioned the free bags...the only real difference between what the Aspire and Executive pages listed then was the 25% versus 50% mile bonus, and I remember being a little surprised that the Aspire benefits were pretty much identical to Executive other than the 25% versus 50% bonus. The current page of Aspire benefits is clearly shorter than the Executive benefits.

As for free bags included when upgrading to Signature, that would be problematic because the Signature upgrade is so much lower.

Two checked bags is $40 on AirTran, and the upgrade to Business Class on AirTran is $49-$129 per segment. So if a customer buys and upgrade and checks two bags for free, AirTran is still netting between $9 and $89 per segment for upgrading the passenger.

Two checked bags is $50 on Midwest, but the current upgrade fees to Signature are $20, $35, or $50 per segment. For a customer checking two bags to Denver, Midwest would be paying them $15 to upgrade to Signature (pay $35 upgrade fee to save $50 in baggage fees).

The alternative would be to raise Signature upgrade fees enough to cover the lost baggage revenue, but that means everybody pays roughly double the upgrade fee for Signature no mater how many bags you check or if your bag fees even apply. This way it's more a la carte in pricing, and more affordable.

Finally, regarding the free checked bags for full-coach on Frontier, I don't think it's quite that way. Let's say these are the fare buckets in a particular city pair:

Fare buckets for AAA - BBB
Y $310
B $265
K $190
V $150
Q $120
W $90
X $75

It's not Y, B and K fare buckets get free bags and others don't. Rather from whatever fare level is the cheapest you can buy three versions of that fare..."economy" is the cheapest fare, "Classic" is that very same fare plus an upcharge, and "Classic Plus" is that very same fare plus a bigger upcharge.

The upcharge to Classic or Classic Plus buys you a bundled set of amenities depening on which one you choose...things like a free assigned seat, priority boarding, free checked bags, bonus miles, etc. So if X class is available, you can buy a seat for $75 or you can choose pay the X class fare plus the upcharge to get Classic Plus. If K is the best fare class available, you can buy a seat for $190 or can choose to pay $190 plus the upcharge to get Classic Plus.

I've seen cases where the "Economy" and the "Classic" (not Classic Plus) fares are the same, usually in a walk-up fare situation on a full flight. But the free bags come from buying a "Classic" or "Classic Plus" ticket, and most of the time that's the lowest available fare plus an upcharge.

There's speculation on if Midwest will move to a similar pricing strategy, and perhaps they will. What concerns me most about this, however, is that this bundled delivery method is currently only available if you by at Frontier's web site. If you buy via another means...including the corporate travel tools or travel departments that many business flyers are required to use...there's no way to buy Classic or Classic Plus. You can only buy Economy. Where that is crummy is that Economy doesn't allow you a seat assignment. And Frontier's web site doesn't allow you to come back to your reservation and separately pay for a seat assignment on your own. On Midwest you have the option of coming back to your reservation on their web site and paying for a Signature upgrade, and on AirTran you have the option of coming back to your reservation and paying for a seat assignment. On Frontier, if you buy Economy, that's it until check in.

Hopefully if they do go to the multi-tier bundled pricing on Midwest this can be fixed. Midwest and Sabre put a great deal of effort into making the upcharge-for-Signature option available through delivery channels other than their web site. Hopefully they don't take a step backwards if they adopt the Frontier bundled pricing.