Al Qaeda may be planning new airline hijack attacks similar to the Sept. 11, 2001, terror attacks for later this summer, Fox News has confirmed.
Usama bin Laden's (search) Al Qaeda network (search) was blamed for the 2001 attacks, and interviews with captured Al Qaeda members along with electronic intercepts describe scenarios similar to Sept. 11.
The information, developed in the last few weeks, points toward an attack using hijacked planes as weapons, rather than a traditional hijacking, officials said.
"We continue to investigate this information to determine its level of credibility," said Department of Homeland Security (search) spokesman Gordon Johndroe.
The DHS alerted airline and security personnel to the possible attacks over the weekend, but it has no plans to raise the terror alert level, currently at yellow or "elevated," according to The Washington Post. The last occurrence of the national terror alert level being raised to orange, or "high," was on May 20 prior to the Memorial Day weekend, and also in the wake of terror bombings in Riyadh, Saudi Arabia (search), and Casablanca, Morocco (search).
Officials did not know who in Al Qaeda might attempt any attacks. There was only a general sense that an attack could take place in the late summer, officials said.
"The intelligence community continues to receive information about Al Qaeda's interest in using the commercial aviation system," Johndroe said. "Because of this, the Department of Homeland Security issued an advisory this weekend to the nation's airlines and law enforcement personnel."
According to a homeland security advisory obtained by Fox News, attack venues may include the United Kingdom, Italy, Australia, or the East Coast of the United States due to the relatively high concentration of government, military and economic targets.
"The extremists may plan to identify flights that transited the target country, so that the hijackers would not need visas for those countries," the advisory states.
The terror plot could involve the use of five-man teams, each of which would attempt to seize control of a commercial aircraft either shortly after takeoff or shortly before landing at a chosen airport, the advisory said.
The hijackers may try to calm passengers and make them believe they are on a hostage, not suicide mission. The hijackers may attempt to use common items carried by travelers, such as cameras, modified as weapons.
DHS stressed that airlines are responsible for abiding by strong security procedures at airports, particularly for those traveling without a visa.
The advisory also states that "based on this notification" no change to the threat level is "anticipated."
"We advised airline and law enforcement personnel to take a look at all their practices and initiate additional measures they may feel are necessary," Johndroe said.
A DHS official told the Post that part of the reason so much attention has been devoted to buttressing commercial airline security is Al Qaeda's tendency to return to patterns of attacks it has mounted in the past.
Since Sept. 11, a number of new security measures within the airline industry have been installed to prevent similar attacks. Reinforced cockpit doors were installed, more baggage screeners were hired and the process was federalized, and items such as silverware are no longer available once a traveler goes through security screening.
Some experts said this latest warning is nothing new, noting that the White House continually receives information regarding possible threats to the airline industry and other sectors.
"I think this is just a routine warning," said Ret. Lt. Col. Bill Cowan, a Fox News military analyst. "They want to warn the aviation community quietly, warning them that something may happen."
William Daly (search), a former FBI investigator and current senior vice president of Control Risk Group, agreed that since the intelligence is nonspecific and coming from a few, non-confirmed sources, the government's warning "is more of a heads up to the airline industry … but it doesn't require us raising the national level."
Daly said the impact Sept. 11 made might be just the impetus Al Qaeda needs to try something similar again.
"It's worked well for them and as tragic as it was, for them, it was a success" in terms of the economic impact and death toll, Daly told Fox News.
Despite the precautions the United States has taken in regards to the airline industry since that day, Daly said, more thought has to be given to alternative methods of attacks.
"We have to start thinking outside the box," he said. "We've taken very strong and very straightforward steps to protect these attacks from happening like 9-11, but when we have info like this … it may support us in opening up our minds … and not be creatures of habit and say 'this is working, we don't have to try anything else.'"
Other experts agree that the United States cannot relax its stance on security and will always have to be watchful, particularly because of all of the global issues the United States has its hand in right now.
"There's enough people that … will try to find an opportunity to hurt America and we have to prepare ourselves for that," Juval Aviv, a former counterterrorism intelligence officer and author of "The Complete Terrorism Survival Guide," told Foxnews.com in a recent interview. "We can't just say, oh it's been quiet for a few months, a year after 9-11, nothing's going to happen."
Being prepared for all sorts of possible terrorist scenarios will best prepare the United States for anything that comes this way, experts said.
"They [Al Qaeda] sometimes want to come back and say 'oh yeah? You think you've taken care of the problem.'"
U.S. officials told the Post on Monday that there was new evidence of threats. The Associated Press later reported a similar story. Homeland security officials confirmed to Fox News that the stories were true.
Fox News' Mike Emanuel, Liza Porteus and Anna Stolley and The Associated Press contributed to this report.