It's been a long road -- make that flight path -- back for Grupo Aeroportuario Del Sureste (NYSE:ASR), sometimes known as Southeast Airport Group or the Spanish acronym ASUR.

The Mexican airport operator, whose crown jewel is Cancun International Airport, reported Q3 earnings that were far less than those reported for the same period last year. The firm earned only $0.25 per U.S. depositary share, versus $0.53 per share in the 2005 quarter.

The reasons are simple enough to see. While total passenger traffic was up 2.3% year over year, international traffic, which earns more money for the company, was down by nearly 1%. And while domestic traffic picked up some of that slack, pronounced public demonstrations in Oaxaca held it back, cutting traffic there by 20%.

The top line showed a 1% decrease, but the decrease in internationally linked commercial revenues was 23%. There was a steep decline in lucrative revenues from banking and currency services, exacerbated by the August expiration of one of the airport's banking contracts. Duty free services increased 5% on a comparable basis but looked bad next to last year because of a one-time legal payment collected in the prior-year quarter. To the positive, the increased passenger traffic did lift retail revenues by 14%, and there were high single-digit and low-teen gains in other revenues, including parking, ground transport, and car rentals.

That probably explained why the stock did so little on the heels of what looks like a 53% cut in quarterly earnings per share. Mr. Market seems to realize that traffic is variable, and it appears there's still a hangover from the late-season hurricanes in 2005. As I've mentioned before, even without one-time items gumming up quarter-to-quarter comps, the airport biz is a leverage game. When there are plenty of vacationing internationals patronizing airport services and spending up a storm, profitability moves quickly to the plus side. When travel is stagnant, it moves the opposite direction with equal speed.

But over the long haul, I still believe this is a very solid international investing idea. There are precious few opportunities to buy monopoly toll bridges to the most desirable destinations in the world. ASUR produces predictable, if lumpy, free cash flows and pays much of that back to investors in dividends.

And luckily for airport shareholders, the airports don't have to go it alone post-disaster. In fact, the costs of reattracting passengers to these exotic locations are often borne by the travel agencies, hotel operators, tour bookers, and airlines. If you think the travel industry is a good bet, you'd do well to look past the obvious names like Expedia (NASDAQ:EXPE), (NASDAQ:PCLN), ContinentalAirlines (NYSE:CAL), Southwest Airlines (NYSE:LUV), or JetBlue (NASDAQ:JBLU) and take a look at ASUR.

In fact, cash flow generation, monopoly position, and the inevitability of travel is one of the reasons we keep a close eye on ASUR for our new international-investment service, Motley Fool Global Gains. A free trial to our latest recommendations -- and a world of possibilities -- is just a click away.

At the time of publication, Seth Jayson had shares of ASUR but no positions in any other company mentioned here. View his stock holdings and Fool profile here. See what he's Digging these days. JetBlue and are Motley Fool Stock Advisor recommendations. Fool rules are here.