John Young reports on BA's tougher stance on mid-air misbehaviour

In Manchester, a drunken teenager who "erupted" into violence on a holiday jet was jailed for 18 months.

The Virgin plane had to be diverted because of the pilot's concern.

Meanwhile in London, a 24-year-old woman received a slightly shorter sentence for causing trouble on a British Airways flight.

Crew are trained to deal with violent passengers

She had also been drinking and had taken the heroin substitute methodone.

BA says there has been a significant increase in 'air-rage' attacks, while the judge in the Manchester case said "these sort of cases are occurring with depressing frequency".

Fight with father

The incident involving David Wilkie, 19, started when his accountant father asked airline staff to stop giving his "loud and abusive" son free alcohol.

The jet from Manchester to Florida was packed with passengers as Wilkie headbutted the older man and then threatened to jump through an emergency exit.

BBC correspondent Catherine Marston reports on the BA case

He then bit a steward on the arm, and spat blood and saliva into the face of a stewardess.

Wilkie also threatened to slit the throats of staff, and smashed a seat before breaking free of an in-flight restraint.

It took more than 40 minutes to calm him down, and the concerned pilot diverted the jet to New York.

Wilkie, from Glasgow, broke down sobbing when he was jailed for 18 months.

He pleaded guilty to endangering an aircraft and assaulting one of the crew.

'Unique' drink aversion

The court heard that psychiatric examinations have since shown Wilkie suffers from what his defence counsel called a "rare if not unique" aversion to alcohol.

"He has a sensitivity to alcohol which reduces him to a state of temporary insanity."

Roger Stout admitted this was not a defence, but added that Wilkie had already been receiving counselling.

He said Wilkie only drank on the flight because he was nervous.

Handcuffed passenger

Crew who were headbutted and kicked: glad its over

In the other incident, Elizabeth Ann Elliott, 24, was jailed by Isleworth Crown Court in west London after an incident that led to her being handcuffed by BA cabin crew.

She pleaded guilty to endangering an aircraft and two counts of actual bodily harm and was jailed for 15 months, with half that time suspended.

This incident began when Elliott, who had flown out to the US was turned back by customs who considered she did not have enough luggage or money to be a genuine tourist.

She drank a quantity of whisky before boarding a return flight to Heathrow and was described as being in an "emotional state".

She also took her prescribed methadone.

Five hours into the flight, Elliott became "agitated and abusive" despite the efforts of stewardesses to calm her down.

She headbutted two members of staff before punching, kicking, biting and scratching a stewardess.

Elliot was deemed to have endangered the aircraft because the first officer had to leave the cockpit to help restrain her.

One warning

BA introduced a 'yellow card' system in early September to counter what it sees as a sharp rise in 'air rage', with more than 260 serious incidents on the airline in 1997 alone.

Under the system, rowdy passengers will receive one warning before they are banned from BA.

A spokesman said the airline was "very pleased" with the verdict and stressed it "would not hesitate to take people to court if they behave in this fashion".