US low-cost carrier will make its debut in the international market at the start of July 2014 with Aruba, The Bahamas, and Jamaica the first countries outside of the US to be regularly served by Southwest’s growing fleet of Boeing 737s. The carrier, the largest domestic airline in the US by passenger numbers, will link the international destinations to Atlanta, Baltimore and Orlando although further network growth will likely be announced in the coming months.

In this first phase of the company's international conversion plan Southwest will take over the operation of six existing routes flown by its wholly-owned subsidiary AirTran Airways and relaunch services on one city pair last flown by the carrier in summer 2010. Southwest acquired its former rival to gain knowledge on international markets and to provide the platform for it to make this great leap into foreign airspace.

With effect from July 1, 2014, Southwest will replace AirTran on the daily flights between Atlanta and Aruba and Montego Bay; the daily offering between Baltimore and Aruba and Nassau and twice daily service to Montego Bay and on the daily schedule between Orlando and Montego Bay and weekly rotation to/from Aruba.

While Southwest gains experience in these markets, AirTran Airways will continue to operate its own international flights between Atlanta and Nassau, between Chicago Midway and Montego Bay, as well as flights to/from Cancun, Los Cabos, and Mexico City, Mexico, and Punta Cana, Dominican Republic. By the end of 2014, the business plans to complete the launch of Southwest service to these four remaining international destinations, according to Southwest’s network team.

"Beginning July 1, 2014, Bags Fly Free beyond US borders to Aruba, The Bahamas, and Jamaica," announced Gary Kelly, chairman, president and chief executive officer to employees and media assembled for a news conference at the carrier's headquarters this week. "As our customers seamlessly click through southwest.com to make these historic bookings today, our People celebrate the final lap in the journey to make possible our international future."

"Southwest Airlines democratised the sky from our first flights more than four decades ago. This milestone enables us to reach new territory, new customers, and build upon a four decade foundation of doing right by the travelers who trust our value and our people," he added.

In our analysis below we look in greater detail at each of Southwest’s initial international routes, highlighting the existing O&D demand on the routes over the past five years. AirTran made its debut in most of these markets in late 2009 or early 2010, although the Baltimore – Aruba route did not come online until December 2011. These routes have been served continuously until today with the exception of Orlando – Nassau which only operated between December 2009 and July 2010.

Southwest will be the sole carrier on the three routes from Baltimore but will face direct competition from Delta Air Lines in the two markets from Atlanta and from JetBlue Airways in the Orlando - Montego Bay and Orlando – Nassau route pairs; the latter is also flown by Bahamasair.

You can find out more about Southwest Airlines' developments by watching our EXCLUSIVE interview with Robert E. Jordan, executive vice president and chief commercial officer at Southwest Airlines and president of AirTran Airways, from last year's World Routes, where he discussed low-cost airlines, budget mergers, network integration, international developments, and how the pioneering airline plans to take things to the MAX with Boeing’s latest short-haul jet.