Mexico's Hot for Low-Cost Carriers

Additionally, privately held Spirit Airlines flies to a dozen Caribbean destinations, including Cancun, primarily from its hub in Fort Lauderdale.

At the moment, the carrier don't threaten to make much of a dent in U.S.-Mexico service. Continental Airlines (CAL Quote), the biggest player in the market, operates 561 flights a week to 30 Mexican destinations, including 523 flights from Houston and 38 from Newark.

On Wednesday, in an indication of the benefit that international alliances bring to legacy carriers, Continental said it would code-share with Alitalia on flights between its Newark hub and Mexico City, Montreal, Quebec and Ottawa. The flights will connect in Newark with Alitalita flights serving Rome and Milan.

Aviation consultant Bob Mann says the low-fare carriers will tread carefully as they enter international markets, seeking "select markets where you can get relatively quick clearance processes."

He says that Canada isn't as attractive as Mexico because the markets are smaller and less leisure-oriented and because Air Canada is a tough competitor.