Travelers can expect longer lines at security checks, random vehicle searches, and an increased presence of law enforcement officers at the nation's airports this week in light of the recently attempted terrorist attacks roiling Britain.
Officials at airports across the country told ABC News that security measures are being stepped up in ways both visible to the public, including more K-9 units and uniformed officers patrolling terminals, and in ways less visible like cargo screenings and the use of plain-clothes agents.
Officials said that security would normally be increased around the Fourth of July holiday and noted that although the "national threat advisory" remains at code yellow or "elevated," airports have been at code orange or "high," since last August.
Michael Chertoff, secretary of Homeland Security, told ABC's "Good Morning America" that while there is no "specific credible information about an attack directed against the United States," authorities have nonetheless "taken some steps to implement pre-existing plans to increase security at our airports and our mass transit and other transportation centers."
"That's partly a reflection of what happened over the last few days," he said, referring to the recent events in the U.K, including a botched car bombing at the Glasgow airport in Scotland over the weekend. "It's partly a recognition of the fact that during the heavy travel, there will be crowds and we want to be prudent and take some extra precautions. But there is no specific threat that we're aware of at this point."
On Saturday two men -- one Jordanian, the other Iraqi -- were arrested in Glasgow, Scotland when they tried to drive a flaming Jeep Cherokee laden with gasoline canisters into the airport there. Six more people have since been arrested for suspected involvement in Saturday's attack and two foiled car bombs found in London on Friday.
As a result, security officials both at U.S. airports and at the Transportation Security Administration said new attention was being focused on the outside of the airport and in areas with vehicle traffic.
"We're doing the same things we always do, just more of it," said TSA spokesperson Ellen Howe.
"People will see more uniformed transport safety officers and more K-9 units. But we're also going to take things outside. We'll be patrolling airport perimeters and parking lots and randomly checking vehicles," she said.
As a result of heightened measures focusing on cars, officials at New York's airports are encouraging travelers to take public transportation.
"We're going to be stopping and inspecting cars, so we're telling folks to use mass transit and allow for extra time," said Pasquale DiFulco, a spokesman for the Port Authority Police.
DiFulco said there would be a visibly increased police presence at area airports but said it was department policy never to disclose the total number of officers working at any one time.
Travelers at New York's JFK airport described a heightened police presence.
"It seemed as though there was kind of a military police presence there, there were some that appeared to be military officers walking around with guns, I guess since it was the international section at JFK," Phillip Blumenthal told ABC News on his way back from Tel Aviv.
Officials at airports in Seattle, Atlanta, Los Angeles and Washington D.C. all told ABC News.com that they were following a TSA directive to increase visible security and random vehicle searches.
"Los Angeles World Airports police officials are in contact with Glasgow officials and are continuously seeking updates from them," LAX said in a statement.
"As always," the e-mailed statement continued, "our random checkpoints continue to screen vehicles entering the airport for contraband and explosive materials."
Jerry Hauer, an ABC News consultant and former director of New York City's Office for Emergency Management, said changes to airport security would impact travelers dramatically.
"There will be a big impact on travelers at airports. There will be less opportunity to drop people off or wait for them at terminals [and] increased police visibility both inside and outside. … At this point in time we're going to have to expect these sorts of inconveniences at airports, at monuments, and at large gatherings," he said.
Hauer said the government was prudent in not raising the terror threat level to orange because it had no knowledge of a specific threat. In 2003 and 2004, he said routine raises in the terror level confused people and deterred local law enforcement agencies from taking the threat seriously.
"I think that the secretary is correct in not raising the alert countrywide unless they have some very specific and very actionable intelligence," Hauer said. "In 2003 and 2004 they were going to orange so often that police departments started ignoring it and the public didn't know what to make of it. Before the Department of Homeland Security goes to code orange it should make sure there is something people really need to be concerned about."
Hauer also said that people should particularly vigilant at large gatherings during the Fourth of July.