All appeared normal at Miami International Airport on Friday despite the State Department issuing a global travel alert.
When asked Friday morning, a Miami-Dade police officer and an airline employee hadn't yet heard about the alert.
The State Department said al Qaeda may launch attacks in the Middle East, North Africa and beyond in coming weeks, and the U.S. government prepared to close embassies and consulates in the region Sunday as a precaution.
"At the end of Sunday, they will re-evaluate whether they are going to be open or not," said Brad Garrett, a spokesman for Miami International Airport. "It's a day at a time thing, I believe."
Passengers arrived at MIA from other countries didn't notice any security changes.
"If they're closing down embassies overseas in Europe, obviously they have some information," said Edward Farbman.
According to three CNN sources, the United States has information that al Qaeda in Yemen was in the final stages of planning for an unspecified attack.
One of the sources said the preparations appeared to have increased in recent days with the approaching end of the Muslim holy month of Ramadan, while a U.S. official noted it was unclear whether the plot would be directed at a target inside Yemen or elsewhere.
While the worldwide alert applied to any U.S. citizens abroad, it specified that the main region of concern was the Middle East and North Africa.