Khaled Khayat, 51, was found guilty in May of conspiring, between mid-January and late-July 2017, to prepare or plan a terrorist act

Two terrorist brothers have been jailed for decades over a plot to blow up an Etihad plane with a bomb hidden in a meat grinder.

Khaled Khayat, 52, and Mahmoud Khayat, 34, were found guilty earlier this year of conspiring between January and July 2017 to prepare or plan a terrorist act.

Khaled was jailed for for 40 years and Mahmoud for 36 years, with non-parole periods of 30 years and 27 years respectively.

The plot - which included their older brother Tarek Khayat who fought for ISIS in Syria - involved blowing up the plane and carrying out a poisonous gas attack.

A bomb hidden in a meat grinder was to be put into the luggage of their unsuspecting brother Amer Khayat, who was flying to Abu Dhabi with 400 others.

But the plan was abandoned when the luggage was found to be overweight at Sydney Airport.

Khaled Khayat (picture centre) proposed that he himself would arrange to take the bomb

Justice Christine Adamson handed down the sentences in the NSW Supreme Court on Tuesday.

Their motivation was said to have included supporting violent jihad and they were accused of doing many preparatory acts during the seven-month conspiracy.

When the original plan failed, Khaled Khayat proposed that he himself would arrange to take the bomb.

'The controller told him not to do that because he had to stay for the continuation of the work here and had to find someone else,' prosecutor Lincoln Crowley QC told the trial.

The second plot involved poisonous gas which the older brother was going to make at his home following instructions given by the controller.

When Khaled Khayat was arrested police found a piece of paper in his wallet that had Arabic words, numbers and symbols written on it.

The paper was examined by a forensic chemist and Arabic interpreters, who determined that one side of the paper included the correct chemical equation for poisonous gas, while the other side had further details relating to the gas.

In his three-day police interview, Khaled Khayat spoke of walking into the airport with the concealed bomb.

The second plot involved poisonous gas which the older brother was going to make at his home following instructions given by the controller. In his three-day police interview, Khaled Khayat spoke of walking into the airport with the concealed bomb (stock image)

He said when he saw children at the airport he thought 'Don't do it, don't be stupid, don't do it' and removed the bomb from the baggage.

But his barrister, Richard Pontella, told the jury that contrary to what his client told police, he never took the bomb to the airport and was actually trying to prevent a terrorist attack.

Mahmoud Khayat's barrister Bruce Warmsley QC said Khaled Khayat had admitted to police taking the bomb to the airport to put in Amer's luggage.

But his client told police he went to the airport with his two siblings to see one of them off.

'He was not aware one of his brothers was intending to murder the other brother by putting a bomb in his hand luggage,' Mr Warmsley said.

Mahmoud Khayat's barrister said Khaled Khayat had admitted to police taking the bomb to the airport to put in Amer's luggage (stock image)

Justice Christine Adamson will hear sentencing submissions on a later date.

A few hours before his brother was found guilty in Sydney, Amer Khayat was acquitted by Lebanon's military court, Reuters reports.

It reported Lebanon's state news agency NNA said Amer Khayat would leave Roumieh prison, where he has spent two years and two months, on Thursday night.

The military court also sentenced the three other Khayat brothers - Khaled, Mahmoud and Tareq - in absentia to hard labour for life, NNA said.