But after cutting back on the vodka, he and his friend started to fight, and when spoken to, Lennon threatened to hit the cabin crew before telling one of them to “F-off.” .
Because Lennon continued to disrupt, the captain decided to divert to Bristol, where police were waiting backstage.
The hijacking landed on Ryanair at a cost of almost £ 6,000.
Lennon, 22, whose address was given as Baldoyle in Dublin, has pleaded guilty to being drunk on a plane.
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The court heard that he had not cooperated with his legal team, had been absent and was in Ireland or Italy.
Judge Michael Longman found he was legally able to process and imprison Lennon in his absence, and jailed him for four months.
The judge said: “One can imagine that his behavior was alarming, in an enclosed space and at altitude, and such that he caused annoyance and disturbance to a number of passengers. ”
The judge ordered Lennon to pay Ryanair £ 5,893.09, covering his entire diversion bill.
He said Ryanair should be made aware of the outcome of the case and that they could decide whether they want to ban Lennon from flying with them.
Mark Worsley sued, said everything was fine when the flight started, until staff noticed Lennon and his friend were drinking their own alcohol, drunk and arguing.
The court heard when staff spoke to them, Lennon threatened to hit them, and the two men were separated.
Lennon then told a cabin crew member to “F-off,” Mr. Worsley said, and the pilot issued a message reminding passengers not to drink their own alcohol on board and to comply with cabin crew rules.
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Due to the continued disruption, the captain decided to divert the plane to Bristol, where police, airport security and fire services were waiting.
Mr Worsley said: ‘The police got on the plane and Mr Lennon immediately presented his hands for handcuffs.
“He got off the plane.
“He was clearly drunk and mischievous and had a half-empty bottle of vodka between his knees. “
Lennon was questioned the next day, said his companion bought the vodka and denied threatening to hit the cabin crew.
Mr Worsley told the court: “He said his behavior was unacceptable. It is clear that the others on board were worried about what had happened. ”
He added that the authority stipulates that those convicted of being drunk on a plane should expect a custodial sentence.