Just three days after Midwest Airlines retreated from most of Florida, rival AirTran Airways jumped in to fill the gap. AirTran announced plans Wednesday to beef up flights to Midwest's Milwaukee hub from the Sunshine State. At Tampa International Airport, where Midwest is keeping its daily Milwaukee flight, AirTran will go head to head by expanding its seasonal service to a year-round schedule. TIA also got good news from JetBlue Airways. Executives said Tuesday the airline would freeze growth plans for the fourth quarter. But JetBlue said that won't affect new flights between Tampa and White Plains, N.Y., set to start in November, or a new route to Cancun, Mexico, that could begin in December, pending approval by the Department of Transportation.