AirTran

Three iterations of an airline: First, it was ValuJet, then AirTran and, in December, it will become Southwest. (Greg Gibson / Associated Press; Joe Kaleita / Orlando Sentinel; Karen Bleiera / AFP/Getty Images)

AirTran Airways is set to fly into the history books Dec. 28 when it makes a final flight from Atlanta to Tampa, Fla. AirTran Flight 1 will retrace a route that's a nod to the airline's first flight in October 1993.

The carrier, now owned by Southwest Airlines, started life as budget carrier ValuJet Airlines, primarily serving the East Coast. A 1996 crash of one of its jets in the Everglades killed all 110 people on board and grounded the airline for several months. Shortly thereafter, the company merged with AirTran and changed its name.

Southwest bought AirTran in 2011 for $1.4 billion. The move gave Southwest 15.7% of the domestic market, according to data from February 2013 to January 2014. That makes Southwest the second-largest U.S. carrier; Delta Air Lines was first with 16.3%, and United third with 15.6%.

Since the merger, the two carriers have operated separately. That is scheduled to change as the airlines become one by the end of the year. Southwest is repainting AirTran's Boeing 737 jets and selling smaller planes in the fleet to Delta, the Associated Press reported.

Southwest picks up AirTran's routes and becomes an international carrier starting July 1, with flights to Nassau, Bahamas; Montego Bay, Jamaica, and Aruba. It also begins flights to Cancun and Los Cabos in Mexico on Aug. 10.

Southwest on Wednesday announced that passengers can use mobile boarding passes on their smartphones or other electronic devices when they go through airport security checkpoints. The pilot program that began last year in Austin, Texas, is now available to all U.S. passengers.