Delta merged with Northwest, United bought out Continental and assuming the US Airways deal to merger with American Airlines goes through, are there any other mergers left to discuss?

Why yes there is--with everyone focused on the big airlines, no one remembers that Southwest added to their company portfolio by buying AirTran.

The airline that offers low-fares with free bags and limited blackout dates, have announced that they are finally going to begin connection flights with its subsidiary.

That comes more than 20 months after Southwest closed on its deal to acquire its one-time rival, offering customers one of the most-tangible changes yet in a merger that has progressed at a plodding pace, according to USA Today.

This will really help the passengers as they can now book single-ticket connecting itineraries that include flights on both Southwest and AirTran.

USA Today gives a good example by explaining how a passenger flying from Akron-Canton will soon be able to buy a single ticket to Salt Lake City that includes an AirTran flight to Denver with a connection on Southwest to Salt Lake City.

Adding, such itineraries previously had not been possible on Southwest and AirTran, even though the airlines' merger closed in the spring of 2011.

Southwest, according to USA Today, said it began testing linking itineraries with AirTran in a five-city "initial phase" that began Jan. 26. Southwest dubbed that test - which focused Atlanta, Fort Lauderdale, Fort Myers, Louisville and Norfolk - a success, saying it's now ready for a broad expansion of the effort.

Southwest will roll out the next phase on Feb. 25, reported USA Today, when it and AirTran will connect their flights options in 39 more cities. Southwest adds, its "on pace" to fully connect the airlines' combined 97 destinations, including international, by the end of April.

"Connecting the networks is a priority in 2013 and a major milestone as we work to combine our two Companies," Bob Jordan, Chief Commercial Officer at Southwest Airlines and President of AirTran, said in a statement, according to USA Today.

"With a connected network, we can offer Customers more itineraries, more destinations, more low fares, and a taste of what's to come once the integration is complete," stated USA Today.