Another month, another million passengers moving through the airports operated by Grupo Aeroportuario del Sureste, better known as ASUR (NYSE:ASR). The granddaddy of the now-popular, publicly traded Mexican airport groups released February traffic numbers that show a 26.6% increase over February 2006 levels.

But as I've explained in previous ASUR updates, I think it's more instructive to compare the current year's results with the 2005 tallies, to see past the now-flattering comparisons against 2006's periods, which were still suffering from post-hurricane syndrome.

This year's February traffic totals represent a solid, if not awe-inspiring, 5.4% gain over the February 2005 numbers. That should inspire some yawns, which is a good thing.

Despite more recent investor excitement about these airport groups -- driven by the post-IPO gains at Grupo Aeroportuario del Pacifico, or "GAP," (NYSE:PAC) and Grupo Aeroportuario del Norte, or "OMA," (NASDAQ:OMAB), they still operate a bit below the radar. I'm not sure everyone appreciates how well small increases in traffic (and the usual revenue upticks that follow) can translate into robust cash-flow growth.

Of course, the leverage works both ways. During slack times, be prepared to see the pendulum swing in the opposite direction.

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At the time of publication, Seth Jayson had shares of ASUR but no positions in any other company mentioned here. See his latest blog commentary here. View his stock holdings and Fool profile here. Fool rules are here.