Q. While booking airfare from Minneapolis-St. Paul to Mazatlan, I was warned by two travel agents that my friend wouldn't be allowed on the plane as her passport expires in fewer than six months, yet no one could cite the source of the rule. Could that be true?
A. Each country sets its own requirements for entry. If an airline believes a passenger won't be able to stay in the country to which it is flying, it will deny boarding. But your friend doesn't need to worry. While some countries require that a passport be valid for a certain amount of time beyond the period of the stay, Mexico is not one of them.
According to the website of the Mexican Embassy to the United States, all U.S. citizens flying into Mexico must present a valid passport. There is no mention of the passport's expiration date. A call to the Consulate of Mexico in St. Paul confirmed that you need only a valid passport.
As a sort of insurance policy, you could print out the entry requirements from the embassy website and bring it to the airport. You will find the fact sheet, titled "American Citizens Services Information for Travelers to Mexico," at http://mexico.usembassy.gov/eng/eacs_sheet.html.