American airports are increasing security measures across the country in the wake of dual terrorist attacks in Paris and the publication by al Qaeda of what counterterrorism experts say appears to be the most detailed, and potentially lethal, bomb recipe ever to be sent to their followers. The top security chiefs for major American airlines have been briefed about the troubling publication, according to a senior U.S. law enforcement official. Department of Homeland Security Secretary Jeh Johnson said Monday the Transportation Security Administration has stepped up random searches of travelers and carry-on luggage in addition to enhanced screening that was ordered this summer at “certain foreign airports.” Johnson said there is “no specific, credible threat” of an attack on the U.S. like what happened in Paris last week, but said that incident, along with others in Canada and Australia, and “the recent public calls by terrorist organizations for attacks on Western objectives, including aircraft, military personnel, and government installations and civilian personnel” made the need for increased security at American airports and elsewhere “self-evident.” The bomb-making recipe, published in the most recent edition of the al Qaeda in the Arabian Peninsula (AQAP) English-language magazine in December, is a detailed guide to making the explosive, getting through security and even where to sit on the plane. “We spared no effort in simplifying the idea in such we made it ‘another meal prepared in the kitchen’ so that every determined Muslim can prepare,” the magazine says, in an apparent reference to earlier versions of bomb-making instructions called “How to Build a Bomb in the Kitchen of Your Mom.” “This group, AQAP, is absolutely determined… to try and [carry] out an attack on a U.S.-bound airplane,” said Matt Olsen, former Director of the National Counterterrorism Center and current ABC News consultant. “The prospect of AQAP trying to get a bomb on an airplane has been, for the past several years, at the top of the list for concerns of the U.S. counterterrorism community. After reviewing the recipe, explosives expert Kevin Barry said it appeared to be one of the most “sophisticated” non-metallic explosives devices he’s seen, which could especially be a problem for smaller airports that don’t employ high-tech body imaging security devices. AQAP, the al Qaeda branch based in Yemen, previously attempted to bring down an American airliner on Christmas Day 2009, but the would-be bomber couldn’t get the device to detonate. That bomber, Umar Farouk Abdulmuttalab, reportedly crossed paths in Yemen with one of the men who executed the Paris terror attack last week. Last week the State Department updated its Worldwide Caution travel alert to all Americans abroad. “Recent terrorist attacks, whether by those affiliated with terrorist entities, copycats, or individual perpetrators, serve as a reminder that U.S. citizens need to maintain a high level of vigilance and take appropriate steps to increase their security awareness,” the alert said. ABC News