Khaled Khayat, 51, conspired to bring down the Etihad flight from Sydney to Abu Dhabi in July 2017, a jury has ruled. He had pleaded not guilty.
The plot was aborted when a bag holding the bomb was too heavy to be checked in at Sydney Airport, local media said.
He can be sentenced to life in prison.
The plan was to blow up the flight carrying 400 passengers with military grade explosives concealed in the grinder.
Police had accused Khayat, and his brother, Mahmoud, of also planning a chemical gas attack in Sydney.
“The jury this afternoon returned a guilty verdict for Khaled and is still deliberating in respect of Mahmoud,” a spokeswoman for the New South Wales Supreme Court was quoted by Reuters news agency as saying.
Khayat’s lawyer, Richard Pontella, argued that his client had in fact been trying to prevent a terrorist attack.
But a jury rejected his argument after three days of deliberations.
Police said the explosives used to make the bomb had been sent by air from Turkey as part of a plot “inspired and directed” by IS.