DALLAS — AirTran Airways and Frontier Airlines have launched summer fare sales that offer the best deals for customers who can travel during the middle of the week.

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AirTran said Tuesday its sale would run through April 14 and cover travel between April 15 and Nov. 2, with the cheapest prices on Tuesday and Wednesday flights. There are more than 30 blackout days when sale prices don't apply.

The airline is touting fares such as $158 per round trip between Baltimore and Bermuda or Florida, and $198 on Atlanta-Washington and Boston-Fort Myers, Fla., trips.

Frontier says it's offering some seats as low as $78 round trip for travel Mondays through Thursdays between June 1 and Sept. 8. The cheapest deals are out of Milwaukee, with most round trips from Los Angeles, San Francisco and Dallas starting anywhere from $188 to $328.

The airlines say those fares aren't available on all flights, and they don't say how many seats they will sell at sale prices.

Tom Parsons, CEO of travel website BestFares.com, said bigger airlines including United, Continental, Delta and American were matching the AirTran sale — probably reluctantly. The airlines have been trying to raise prices to offset high jet fuel costs, and a new sale undercuts that effort.

"This is Christmas in April," Parsons said. "Many people didn't think they were going to get summer fares this cheap."