A MAN who described himself as a "Jack of all trades'' has been fined for exposing himself and masturbating in front of a woman on a Darwin-bound flight.

Lucas Steven Knudson argued he was "just adjusting himself" because his jeans were too tight, a Darwin court heard yesterday.

The case follows hot on the heels of a recent front page NT News report in which a court heard a Territory man filmed himself masturbating while speeding at 150km/h in his Holden SV6.

In yesterday's case, the Darwin Magistrates Court heard Knudson, 32, had just landed on board Virgin Blue flight DJ449 from Brisbane when he was escorted off the plane by Australian Federal Police after masturbating for "maybe four minutes" underneath his tray table in view of Kununurra mother-of-two Simone Holt.

The court heard the Ballina man - wearing jeans, a flannelette shirt, white socks and thongs - told airport officers her story was "bull****".

But the two police officers who spoke to him after the midnight flight on April 11 said his jeans were not "overly tight".

After a two-hour hearing, magistrate Tanya Fong Lim found Knudson guilty of committing an indecent act on the plane under the Commonwealth Crimes Aviation Act.

Ms Holt was emotional as she told the court she awoke about three hours into the flight to see Knudson masturbating.

The Grade 3 teacher's aide said she was seated on a window seat in row 11 with no one between her and Knudson in the aisle seat - and he was shielding his activity from other passengers and flight attendants on the other side with his shirt. Ms Holt said she turned her reading light on to indicate she was awake and he "should cease" the act.

She said he did stop "somewhat" but left his genitals exposed outside of his jeans.

Ms Holt - who had to describe every detail of what she had seen in court - said she became anxious and signalled a flight attendant and asked to be moved.

Virgin Blue flight attendant Kelly Taylor said Ms Holt was "panicked" and breathless when staff tried to console her at the back of the plane. She said Knudson had stretched out across all three seats to sleep with his fly undone.

On the witness stand, Knudson said he had undone his button and touched his genitals for a few seconds to make himself more comfortable.

Knudson - who described himself as a "jack of all trades" - was travelling to Darwin to work at a Territory crocodile park. He sang in court as he waited for his hearing to start - but was shaking when he was found guilty later yesterday afternoon.

Ms Fong Lim said it was totally unacceptable to masturbate in public, "particularly in an aeroplane situation" and fined Knudson $2500.