WASHINGTON – There are no plans to raise the national terror alert status, despite highly publicized warnings that Al Qaeda (search) may try to repeat the airline hijackings of Sept. 11, 2001, federal officials said Tuesday.
"The hijackers may try to calm passengers and make them believe they were on a hostage, not suicide, mission," read an advisory warning distributed this past weekend to airlines and law enforcement agencies. "The hijackers may attempt to use common items carried by travelers, such as cameras, modified as weapons."
The Department of Homeland Security's (search) advisory added that five-man teams might try to take control of airplanes — and that unlike in the Sept. 11 attacks, hijackers with pilot training would not be needed.
The Sept. 11 hijackers told passengers not to worry about their safety and were believed to have carried weapons then permitted aboard passenger planes.
Officials said the credibility of the latest threats was still being evaluated. There was no precise information when or where such attacks could take place.
A copy of the warning, obtained by Fox News, says an attack could take place by the end of the summer. It suggested cities on the East Coast of the United States, in the United Kingdom, Italy and Australia as possible targets.
"No equipment or operatives are known to have been deployed to conduct the operations," the warning said.
The State Department also updated its "Worldwide Caution" advisory (search) to include the information from the homeland security warning.
"The U.S. government remains deeply concerned about the security of U.S. citizens overseas," the State advisory said. "U.S. citizens are cautioned to maintain a high level of vigilance, to remain alert and to take appropriate steps to increase their security awareness."
It warned that "terrorist actions may include, but are not limited to, suicide operations, hijackings, bombings or kidnappings. These may also involve commercial aircraft. Other potential threats include conventional weapons, such as explosive devices, or non-conventional weapons, such as chemical or biological agents.
"Terrorists do not distinguish between official and civilian targets," it added.
The department urged Americans overseas to monitor local news and maintain contact with the nearest American embassy or consulate.
The national terrorist threat level remained at yellow, signifying an elevated risk of attacks. The five-level, color-coded system was last raised to orange, or high risk, for 11 days in May. As of now, officials don't plan to raise it.
Some complained the government still was doing too little to alert the public and key industries to terror threats.
"Our concern is that there will be bulletins put out that will not be made available to us," said Capt. Jon Safley, president of the Coalition of Airline Pilots Association (search), a pilots union. Safley, who doesn't fly, said he hasn't been getting warnings and wasn't sure all pilots know when advisories pertaining to air travel are issued.
Jim Schwartz, director of emergency management for Arlington County, Va., which includes both Ronald Reagan Washington National Airport and the Pentagon, said his agency had received no warning from Homeland Security. He said he would need more specifics before increasing security based on published reports.
The warning was based on information gleaned from interviews of at least one Al Qaeda prisoner as well as intercepted communications within the past several weeks.
"Cognizant of changes in aviation security measures since Sept. 11, 2001, Al Qaeda is looking for new ways to circumvent enhancements in aviation security screening and tightening immigration requirements," the warning said.
DHS placed a statement on its Web site saying the advisory was transmitted after U.S. intelligence-gatherers "received information that Al Qaeda continues to be interested in using the commercial aviation system in the United States and abroad to further their cause."
Since the Sept. 11, 2001, attacks, Congress has taken a number of actions to limit the possibility of suicide hijackings, including arming commercial pilots, boosting the number of air marshals and hiring an all-federal work force to screen airline passengers.
Last week, House and Senate negotiators agreed to arm cargo pilots as part of a Federal Aviation Administration funding bill (search). The bill also would require that commercial airlines teach flight crews how to deal with terrorists, including self-defense, and Homeland Security and the FAA would have to review security at facilities that repair and maintain aircraft outside the United States.
Lawmakers are expected to pass the bill in September.
Fox News' Teri Schultz and Anna Stolley and The Associated Press contributed to this report.