A man who threatened to break a seven-year-old child's legs for kicking the back of his seat during a flight has been fined $750 by a magistrate who described him as 'childish'.

Brett Walter John Gale, 32, from Brisbane, became increasingly agitated on the Virgin Australia flight between Adelaide and Brisbane on August 30, 2015 as the child kicked his seat.

He plead guilty to offensive and disorderly conduct in Brisbane Magistrate's Court on Thursday, The Courier Mail reported.

Brett Walter John Gale, 32, from Sunnybank Hills in Brisbane was fined $750 after threatening to break a seven-year-old's legs

The manwas seated in the row in front of the child during a flight from Adelaide to Brisbane

Prosecutor Rebecca Blaszczyk told the court Gale exploded at the child just moments after the plane left Adelaide airport, the news report said.

'Stop kicking the f***ing seat,' Gale was quoted as yelling at the seven-year-old.

'Go on, kick the f***ing seat again and I will break your f***ing legs,' he reportedly said.

When the plane landed, Gale directed his anger at the child's mother, directing a stream of verbal abuse and swearing and demanding the mother 'discipline' the child.

He became agitated after the child kicked his seat

When another passenger stepped in and asked him to calm down, Gale grabbed his shirt and threatened him, the court heard.

The magistrate told Gale he should have ignored the child instead of 'inciting' her to continue kicking the seat by his outburst.

He was fined $750.