联邦调查局发布新恐怖袭击警告称，阿尔盖达恐怖组织有可能在恐怖袭击中使用直接飞机。在旅行社和官方就此做出回应时，直升机仍继续起降带着游客鸟瞰曼哈顿区。鉴于恐怖分子可能将直升机当武器的警告，一些机场和直升机驾驶员尔他们可能会采取额外的防范措施。

　　NEW YORK -- Helicopters continued to take off and land Monday, giving tourists a bird's-eye glimpse of the Manhattan skyline, even as tour operators and city officials reacted to new warnings issued by federal officials that al-Qaeda might use helicopters in terrorist attacks.
Some heliport and helicopter operators said they might take additional security precautions because of warnings about helicopters being used as weapons by terrorists.

　　But they emphasized that they have been on heightened alert since the Sept. 11 attacks.

　　Mayor Michael Bloomberg said the potential threat is not new. "You may rest assured that ... if you try to get on a helicopter in New York City, you have to go through a magnetometer or a handheld wand, and they look at your identification and they check everything you carry. That's been going on since 9/11."

　　The FBI and the Department of Homeland Security issued three bulletins Friday to 18,000 law enforcement agencies nationwide warning about the possible use of helicopters, rental vehicles and rented storage facilities by terrorists.

　　One bulletin said that "although there is no credible, specific evidence supporting use of helicopters in an aerial attack in the United States, the threat cannot be discounted."

　　A second bulletin noted that limousines should be more closely scrutinized because they "have larger storage capacity than regular passenger vehicles." It added that with their aura of importance, limousines may be allowed where the public would not.

　　Still, much attention is on New York, where financial institutions were recently the focus of a new terrorism alert and the Republican National Convention will take place at the end of this month.

　　New York City has three heliports used by companies that provide aerial tours. One of the tour operators, Liberty Helicopters, said in a written statement that it was contacted last week by the FBI-NYPD Joint Terrorism Task Force.

　　No details were given on what was discussed.

　　The statement said that since Sept. 11, the company has upgraded its security procedures to include physical screening and a check of passenger identification. It also does not allow sightseers to carry any personal luggage on helicopter tours.

　　The Port Authority of New York and New Jersey, which oversees the Downtown Manhattan Heliport, has also been on alert since the terrorist attacks of 2001. But people now might see "enhanced visibility of our security forces at all our facilities," said spokesman Lou Martinez.

　　One company that ferries individuals into New York City on New Jersey-based helicopters said that police seem to have stepped up their scrutiny in past days.

　　"If I make any movements, immediately a police car will come over, reminiscent of what they did after 9/11," says David Cannella, charter coordinator and hangar manager for Excelaire Service.

　　There are concerns about limousines as well. Ronit Hirsch, an employee for Tri-State Limousine, a service in New York City, said the company is careful and works primarily with repeat customers.

　　"We don't just pick up people off the street," she says.