Two failed terrorist attempts aimed at London's theater district and one successful attack on Glasgow Airport in the past month could have cast a cloud of doubt, if not panic, over international summer travel.
But so far, most British and American travelers have taken the disruptions in stride, refusing to cancel their long-planned holidays despite added delays and extra security measures.
Brian Hoyt, a spokesman for the Internet travel service Orbitz.com, says the terrorist attacks of 9/11 have made "people more resilient.
"They are getting used to the world we're living in," says Hoyt, "and those who know they have to travel through Heathrow and Glasgow want to know what they need to do to get there safe and sound."
Glasgow Airport representative Donald Morrison says it's "too early to say what impact, if any, the attack on Glasgow Airport will have on passenger numbers," but insists "the airport is busy and flights are operating normally."
Airline officials are even more optimistic.
"The summer season is our busiest travel period, and we've seen no decline in bookings or actual travel," Brooke Lawer, a Virgin Atlantic Airlines spokesperson, tells ABC News.
The only drop in numbers can be attributed to flights delayed or canceled in the immediate aftermath of the attacks themselves.
Mark Mann, head of Media Relations for BAA, the company that owns and operates both Heathrow Airport in London and Glasgow Airport, reports that Heathrow -- often a destination for travelers coming across the Atlantic from the United States -- suffered "a fall 2.4 percent loss as over 60 percent of flights were canceled or diverted when the airport was temporarily closed."
Security levels in the United States were increased over the Fourth of July holiday, and Homeland Security Secretary Michael Chertoff recently set off a firestorm of criticism when he told the Chicago Tribune's editorial board that he had a "gut feeling" about a forthcoming terror attack, saying that "we are entering a period this summer of increased risk."
In an interview with ABC News' Pierre Thomas this week, Chertoff downplayed those comments, saying, "We don't have specific intelligence about an attack, that is, a particular attack against the homeland, that is imminent or scheduled for the summer."
Chertoff noted, "It's important as we go into the summer season, which is typically a time people like to relax, to remind people that this threat is very alive, and the enemy is continuing to try to improve itself and carry out its attacks."
Whether those warnings will shake the travel industry is yet to be see, but so far, travelers are taking to the sky with caution but not fear.
"We've been at code orange threat level for domestic and international flights since Aug. 10, 2006, ever since the banning of liquids on airlines," says Darrin Kayser, TSA Manager of Strategic Initiatives.
While the local and international flights are at level orange, or "high" threat alert, according to Homeland Security's Advisory System, the U.S. government's national threat level is at yellow, or "elevated," and reduced significantly from London's current threat level of red, or "critical," according to BBC News.
"Our Visual Intermodal Protection and Response teams have been deployed on a nonpermanent and flexible basis to enhance security at high mass transit and airport locations, including the Fourth of July and Christmas," says Kayser.
These VIPR teams are composed of federal air marshals, surface transportation security inspectors, transportation security officers, behavior detection officers and explosives detection canine teams.
Whether providing extra support on congested holidays or lending their safety expertise, VIPR teams are stationed in cities throughout the United States, including New York, Buffalo and Syracuse, N.Y., Los Angeles, Boston and Providence, R.I., Cape May, N.J., and Martha's Vineyard, Mass.
A significant number of police officers, as well as VIPR members, were added to various larger airports after the July Fourth holiday, including Dulles International Airport and Reagan National Airport in Washington, D.C., and New York's John F. Kennedy International Airport, along with thorough inspections of cars waiting to pick up passengers.
"These teams are always there," says Kayser.