(FORTUNE Magazine) – The busy summer travel season couldn't have got off to a worse start for airlines. The hi-jacking of TWA flight 847 and the rash of terrorist bombings in airports have led some people to think twice about flying overseas. President Reagan warned that it was dangerous to travel through Athens International Airport, where the TWA hijackers boarded the plane, and urged Americans to avoid Middle East countries that do not condemn the hijacking. While some airlines reported a higher number of cancellations on flights to areas perceived as dangerous, most say the incidents are having little effect on passenger loads. For example, Air-India claims cancellations have been no higher than usual. The most immediate impact was beefed-up security at airports and delays at some security checkpoints. At a meeting in Montreal of the International Civil Aviation Organization, U.S. Transportation Secretary Elizabeth Dole announced an end to curbside baggage check-ins for international flights, an expansion of the air-marshal program, spot searches of carry-on luggage, and plans to X-ray air cargo and checked baggage. As a result, business has picked up for airport security firms. Says Richard Wackenhut, senior vice president in charge of operations of Wackenhut Corp., which handles passenger screening at LaGuardia in New York, among other airports, ''It's safe to assume if the federal government orders tighter security regulations, the entire security industry will benefit.''