Professor Barton said there would be "lots of capacity for exploiting the lax security" at Cairo airport and other North African airports where the aircraft had been earlier in the day.
While it would have been harder to plant a bomb at Paris Charles de Gaulle Airport, he said someone could have managed to conceal the device on a previous flight and set it to detonate 30 hours later.
He noted that France and Belgium also had a large IS element, with many individuals returned from the Middle East.
The Middle East expert said the current security situation in Egypt is "dire", with the authorities struggling to maintain control over its citizens.
"The government under Mubarak was repressive, under Sisi [president Abdel Fattah el-Sisi], it's worse. The regimen has totalitarian aspirations but not the capacity to achieve these aspirations.
"They'll pick someone off the street and beat the life out of them. It polarises society. IS has a strong presence.
"Even in Cairo and Alexandria there are elements more inclined than ever to fight back.
They're next to Libya, a failed state that's in chaos, and they don't have complete control over their borders."
The Federal Government's advice online is for Australians to "reconsider your need to travel to Egypt due to the threat of terrorist attack and kidnapping."
It says terror attacks could occur at any time, including in tourist areas.
