abc's john hendren has that story. >> reporter: security experts worry these could become al qaeda's next weapon. an intelligence bulletin from the department of homeland security and the fbi says small planes pose a significant threat to the homeland. there are 228,000 general aviation plans at 4,000 airports across the nation. too many to monitor. small planes like these come and go without all the scrutiny faced by passenger airline jets. as soon as one lifts off here in college park, maryland, it's in view of the capitol, the pentagon and just ten miles from here, the white house. intelligent expert, say al qaeda is no longer determined to pursue only massive 9/11-style attacks. >> they try a lot of smaller attacks, they're just as effective as far as the fear factor. and so they really get more bang for their buck. >> reporter: last year, a man with a grudge against the federal government flew this plane into an irs office in austin, texas. two died in that crash. federal officials fear the next time might be far more deadly. john hendren, abc news, college park, maryland. >>> w