A man has been found guilty of trying to smuggle a pipe bomb on to a plane at Manchester Airport.
The "crude improvised explosive device" was found in Nadeem Muhammad's luggage as he passed security on 30 January.
He was questioned by police but later released. Greater Manchester Police (GMP) said there had been "errors with our assessment of the device".
Muhammad was found guilty of possessing explosives with intent to endanger life at Manchester Crown Court.The 43-year-old, of Tinline Street, was born in Pakistan and holds an Italian passport.
He was attempting to board a Ryanair flight to Bergamo in northern Italy when the item was discovered. He told airport officials that someone else had put it in his luggage.
The court heard how he was questioned by police but not arrested.
He then returned to the airport on 5 February and flew to Italy.
A forensic examination of the device, which was made from batteries, wire, masking tape and a marker pen tube, later found it was "potentially viable", the jury was told.
It was found to contain nitroglycerin and nitrocellulose, which led to Muhammad's home in Italy being searched.
After being questioned by Italian police, he was released and boarded a flight back to the UK on 12 February. He was arrested by UK officers shortly after it landed.
Muhammad wept as the majority verdict of 10 to two was given in court.
Speaking after the hearing, GMP's Supt Graeme Openshaw said based on the "overall circumstances", officers "determined that there was not sufficient evidence or suspicion to arrest [Muhammad] and place restrictions on his movement".
He said once the device had been properly examined, he was "arrested at the first opportunity".
"We accept there were some errors with our assessment of the device on the day and we have already reviewed our practices," he added.
Analysis from Julian Bray, aviation security expert
It was a very small device, but if Muhammad had been sitting near the window, it would have blown a hole in the fuselage and possibly caused the severe depressurisation of the cabin.
The oxygen masks would have dropped down, there would have been a few burst eardrums and it would have been very uncomfortable, but I don't think it would have actually blown the plane apart - it could probably have limped home and landed.
But the point is these things shouldn't happen and there are lessons to be learned from this.
What I cannot understand is that not only did the security officer take the device off Muhammad, he was later allowed to board an aircraft.
The police and the airport security need to understand that in the current situation, you cannot afford for a moment to relax the rules, you must be really diligent.
The Crown Prosecution Service's Sue Hemming said Muhammad's motive "remains unknown", adding: "However, it is clear that the consequences, had he been successful, could have been disastrous."
Muhammad's trial also heard that after the airport terminal's security chief Deborah Jeffrey was made aware of the device, she put it in her pocket before passing it on to police.
She told the court a swab had revealed no evidence of explosives, so she pocketed it so it "wouldn't go missing".
A spokesman for Manchester Airport said the actions of staff had "prevented a potentially dangerous item from being taken on board an aircraft".
"In this instance, the actions of our security team led to the detection of a suspicious device [and] following its detection, our team handed the passenger and the device over to the police to investigate further," he said.
Muhammad will be sentenced on 23 August.