Ibrahim al-Asiri He is Ibrahim al-Asiri, a Saudi militant as well as chief bomb-maker for al-Qaida. He makes use of PETN in bombs that X-ray machines resist to pick up. He is believed to have made the ‘underwear’ bomb used in an endeavor to destroy a US-bound plane in 2009. His most important threat is that he is teaching his methods to al-Qaida apprentices, leading to the ‘credible threat’ warnings stated by the US in July 2014 and caused amplified security on all direct flights.