They've been watching Aero Mexico #490 from Mexico City. I posted this on the AQ thread that's reached about 4,000+ posts now.
"Hours later, the FBI, LAPD and other law enforcement officers also descended upon Aero Mexico Flight 490, which arrived late Christmas Day from Mexico City. The aircraft and passengers on that flight, originating in the Yucatan capital of Merida, also were thoroughly examined. Early in the week, counterterrorism officials told the Los Angeles Times that authorities were paying special attention to Los Angeles bound flights by Air France, Aero Mexico and Air Tahiti Nui for fear that they could be exploited by Al Qaeda".