Despite the State Department's earlier assertion that no Americans were on board Air France Flight 447, it turns out that two U.S. citizens were passengers on the Airbus A330 that disappeared from the night sky on Sunday.

A multinational search is under way for the aircraft, which is only four years old, and its traveler and crew of 228 people, which were headed from Brazil to Paris.

Experts are speculating that massive thunderstorms are the cause of the airliner's disappearance, but French President Nicolas Sarkozy says no hypothesis is being discarded. And although there are no indications of terrorism, there that can't be ruled out yet, according to the Pentagon.