The fact that the massive terrorist attacks in the United States last week were carried out by commandeered passenger planes has prompted the world’s inventors to look for ways to prevent hijackings and their federation is calling for ideas. The International Federation of Inventors’ Associations (IFIA), which is based in Geneva, wants to promote inventions that will make flights safer. The Society of Greek Inventors, which is one of the IFIA’s 109 members, has called on citizens to put their brains to work and submit their ideas. The IFIA will pass on the more effective inventions to aircraft manufacturers and airlines. A Greek national, for example, has thought of a scheme whereby a plane’s pilot will be able to release a hypnotic gas into the passengers’ cabin when a hijacking is attempted. Choosing the right kind of gas, though, will be tricky, so that ailing passengers or children will not be put to sleep forever. The general secretary of the Greek society, Yiannis Sakellaridis, who is an industrial patents lawyer, said that the society (which can be reached at 3611889) will help would-be inventors patent their ideas and promote them with the IFIA.