A man who arrived at a British airport for a flight with a pipe bomb in his hand luggage was convicted Tuesday of trying to smuggle explosives onto a plane.

Nadeem Muhammad, 43, denied wrongdoing after security staff found the device inside the zip lining of his bag at Manchester Airport on Jan. 30. He said the bomb, made from masking tape, batteries and a marker pen tube, must have been planted by someone else.

But prosecutors said he planned to detonate it during a Ryanair flight to Italy.

During his trial, prosecutors also revealed that security officers didn't initially think the bomb was viable. Muhammad was allowed to fly to Italy several days later.

After he departed, a forensic expert examined the device and judged it to be "crude but potentially viable." It contained smokeless propellant, which is normally found in firearms ammunition and made of nitroglycerin and nitrocellulose.

Muhammad, who was born in Pakistan and has an Italian passport, was arrested when he returned to Britain.

He sobbed after the jury found him guilty of possessing explosives with intent to endanger life or property. He is scheduled to be sentenced Aug. 23.

Crown Prosecution Service counterterrorism chief Sue Hemming said after the verdict was returned that "despite extensive investigation, Nadeem Muhammad's motive for attempting to take this device onto a plane remains unknown."

"However it is clear that the consequences, had he been successful, could have been disastrous," Hemming said.