But you can still get its incredible $399 round-trip First Class fares—if you know the number

On Feb. 21, Aeromexico launched a very public and even more incredible fare sale First Class from southern US cities to a number of destinations in Mexico starting at $399, along with miles and elite credit with SkyTeam partners like Delta and Continental. (More northerly US gateways were higher, with Chicago Mexico City coming in at $499 and Boston Mexico City at $599.) The carrier included the fare in travel agents’ computers and gave it to major online travel agencies.

Then, when the big boys matched it, Aeromexico said,“Caramba” and dove for cover. It “pulled” the fare—which was supposed to be good until Dec. 10—from travel agency computer reservations systems, effectively making it disappear.

Now here’s the wrinkle: The carrier left the details on its own website (www.aeromexico.com), but don’t bother visiting you can only get the fare by dialing (800) 237-6639. You must be very specific because there is another First Class promo that is not as good, and you’ll be offered that unless you ask for the $399 round-trip First Class fares.

With fares this low, don’t even think of buying coach and using an elite upgrade, or spending 30,000 miles to save only $100 or $200 (the difference between coach and First on many routes).

Mexico is the new no brainer destination if you need to take a “mileage run” to get to the next elite level or to rack upmiles for future award travel. You can easily rack up a quick 4,000+ miles, in comfort, for peanuts.

The fine print: Non-refundable; $200 change fee; no minimum/maximum stay required. Tickets are issued electronically and must be purchased at booking or at least three days before departure, whichever comes first.

Link to more routes and fares: http://www.aeromexico.com/usa/english/pages/popup/tabla_clase_premier_EN.html