LONDON: A man accused of sparking a security alert on a Pakistan International Airways plane acted like an “idiot” but did not make a serious bomb threat, a British court heard Wednesday.

Mohammed Safdar, 42, and his friend Tayyab Subhani, 30, were arrested in May after their flight from Lahore to Manchester in northwest England had to make an emergency diversion to London's Stansted Airport.

Britain scrambled Typhoon fighter jets to intercept the flight.

The British-born pair deny endangering the plane.

A previous court hearing was told that the men had become aggressive towards airline stewards and had made false threats that the “crew and passengers would be killed and the aircraft blown up before landing”.

But a passenger on the flight told the men's trial in Chelmsford, southeast England, that although Safdar had acted like an “idiot”, he had not made a serious bomb threat and other travellers had not felt threatened.

“I heard the men say jokingly between themselves 'I bet they think there's a bomb on the plane',” Ferzana Rana told the court.

“He was swearing in Urdu and a lot of the words and language were not something anybody would want to repeat.”

Safdar twice told a steward “I'm going to kill you” in Urdu, she added.

But asked if the steward had taken the remarks seriously, she said: “No, it was just an idiotic remark.”

Once on the ground, many passengers expressed annoyance that the flight had been diverted over a “trivial incident”, Rana told the court.

Subhani had encouraged Safdar but had not behaved in an abusive manner, she added.

The men, from Lancashire in northwest England, claim the allegations are made up and that cabin crew encouraged passengers to corroborate their story.

They had been returning from Safdar's mother's funeral in Pakistan.

Prosecutors have stressed that the pair are not Islamic extremists or “terrorists” but that the crew was forced to take the threats seriously.

“Such utterances, if made at ground level, may sometimes be capable of being ignored,” prosecutor Brian O'Neill told the court as the trial opened on Tuesday.

“But when those threats are made in flight at 30,000 feet on a commercial jet, that's not an option.”

Once on the ground, the plane was surrounded by armed police under a full-scale bomb alert. The trial is expected to last five weeks.