Not to be outdone by US Airways’ “sweetened deal” move on Delta Wednesday, Thursday morning it was disclosed that AirTran has sweetened its own hostile bid for Midwest Airlines.

AirTran is now offering to purchase Midwest for about $345 million, an increase of about 18% over its previous offer.

The new offer is the equivalent of $13.25 a share, based on the closing price of Midwest stock on Monday. It’s also a 3% premium on the closing price Wednesday. It’s also just about where most analysts and observers had estimated AirTran would have to move to — if the airline was to have any chance at forcing a deal.

The Midwest board of directors voted “no” in early December on AirTran’s initial offer of $11.25 a share.

Not surprisingly, this time Joe and the folks in Orlando took the deal directly to Midwest’s shareholders, completing ignoring the airline’s board of directors, which has been loathe to discuss a potential merger with AirTran.

According to Joe Leonard, AirTran CEO, “We thought we’d let the owners decide.”

The deal expires on Feb. 8.

My thoughts on this one? I’m not convinced this is as good a move for AirTran as the airline has put forth.

Having said that — at $13.25 a share — this offer is clearly in the range of being one that just might be too good for the larger institutional shareholders of Midwest to pass up. Don’t think that AirTran management has not been in direct contact with them and therefore feel they have a good sense of what it is going to take to get these guys onboard a deal.

I don’t think there’s any question this is going to bring intense pressure from those shareholders towards Midwest management.

And hey — at some point the members of the Midwest management team has to start looking at what they would get out of this deal — and start to think about how nice it would be to see all those dineros in their bank accounts.

Having said that, from an airline standpoint alone — this one is really not a potential match-up we like. I understand why AirTran wants to do it — I’m just not sure it’s going to work out very well for them in the long term — for a number of reasons.

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