What are the advantages and disadvantages of Southwest Airlines going international?

My understanding is that fuel and taxes are even more expensive than in the US. Landing fees, fuel taxes, fuel prices etc are, believe it or not, still more expensive outside the US. Going to Canada and Mexico and some places in the Caribbean would provide international destinations that would NOT require extensive (beyond 160 miles off shore) overwater routes. This would allow SWA to serve those countries without having to go to the expense of equipping the aircraft with life rafts. Currently, SWA has only life vests and seat cushions for flotation devices. Flying beyond 160 miles from shore (or 100 miles if north of about the mid Atlantic states) would require the addition of life rafts to the aircraft, training of aircrew etc. This all costs money. Also, the life rafts weigh quite a bit, so that would lead to greater fuel consumption of even more expensive fuel--a double whammy.

That being said, SWA is running out of lucrative destinations in the US. Atlanta, Minneapolis and Charlotte are the only major metropolitan areas not yet served by SWA. New York City is "semi-served" by the Islip, New York airport, but SWA may need to start serving Laguardia or JFK before too long. There are lots of big cities in Canada, Mexico, the Caribbean and Central America. The cost of serving those destinations will be higher than the cost of serving stateside cities, but if SWA is to continue to grow, it will have to look beyond American shores at some point.

The foreign markets are about the last bastion of profitable routes for the legacy carriers in the US. If SWA begins to serve some those markets, look for prices to come down dramatically as the legacy carriers try to keep SWA out of the game. That affect will not be permanent, though. SWA will not be able to charge rock bottom prices in foreign markets because of fuel and other costs listed above. But it will certainly be able to under-price the legacy carriers because SWA is not carrying billions and billions of dollars in debt like most other airlines are.