The alert was issued by the U.S. State Department on Sunday, as intelligence officials warned Americans in Europe of possible terror strikes aimed at popular tourist magnets in the continent. Britain and Japan also issued the alert for its citizens.
In addition to the airport, other modes of transportation are following suit with heightened security in light of the terror alert.
Amtrak trains will be taking part in a planned exercise this week with beefed up safety measures. Operation RailSafe was actually planned well before the terror alert was ever announced, but it is another area of mass transit where commuters will see more security.
Also, subways in New York City will see more patrols in light of the terror alert. British and French police are also increasing their security presence for transportation hubs and tourist destinations.
Mass transit officials were briefed this week, and out of an abundance of caution, they're beefing up security at least temporarily. The terror alert doesn't come with any specifics as to when or where attacks may be planned, but leaders insist they still have good cause to keep the alert in effect.
"I wouldn't say we have specific information about a particular place or a particular time, and yet we have, I think, specific information that justifies the issuing of the alert," said U.S. Attorney General Eric Holder.
Some travelers seem unfazed by the alert, sticking to their plans to tour the continent and not making any changes.
"I'm interacting with tourists as a tour guide every day, and I have not had any comments. I noticed no real difference, and I haven't heard of anybody altering plans or changing anything," said a tour guide.
The U.S. State Department is not asking Americans to cancel their plans to Europe. However, they are asking travelers to use common sense and be aware of their surroundings and any suspicious activities while in Europe.
The terror suspects reportedly include German and British citizens, who may be of Pakistani or Afghan decent.
Pakistani officials said they believe five German militants were killed in an American missile strike close to the Afghan border. They also said those killed were believed to be German citizens in the region for terrorist training. Officials also believe that one of the Britons died in a recent CIA missle strike.
Intelligence and law enforcement officials claim they have information that terror teams could launch commando-style attacks similar to the 2008 attack in Mumbai, where 175 people were killed after an organized band of extremists went on a shooting spree for three days, targeting high-profile places visited by westerners.
The Associated Press contributed to this report.