"The Australian Government has introduced additional aviation security measures at global and domestic terminals at Australia's major airports", Qantas said in a statement. Qantas, Tiger, and Virgin Australia have also urged passengers to limit the amount of carry-on and checked baggage they bring, to reduce delays in screening.
Passengers taking a domestic flight this week in Sydney, Melbourne, Brisbane or Adelaide have been advised to check in two hours before to allow enough time to get through the heightened security measures.
"I want to thank the travelling public for their forbearance", Mr Turnbull said.
A police spokesman said the men had not been charged as of yesterday morning.
Authorities arrested four men in connection with the plot, The Australian reported.
"The plot that we are investigating we believe was an attempt to put a device onto an aircraft, but beyond that the speculation is just that - it's speculation", Colvin told a press conference Monday.
Australian Federal Police Commissioner Andrew Colvin said on Sunday they have taken the threat very seriously.
The four men arrested can be held for seven days without charge after a magistrate granted police special counter-terrorism powers. They were allegedly plotting to blow up an aeroplane.
Dutton, the border protection minister, urged travelers to arrive at Australian airports two hours before domestic flights and three hours before global flights to allow time for more screening.
"You should infer that we think this was credible and there was an intention, and there was quite possibly a capability as well".
Australia's terrorism threat level hasn't been changed following the raids.
The plotters were apparently making a peroxide-based explosive device rather than using nitrate-based chemicals that can be detected by airport security swab tests, Barton said.
Most flights have been leaving on time despite the delays.
The government says tougher screenings will remain in place until authorities believe they are no longer necessary to address a terrorism threat.
A source at a major Australian carrier said airlines and airports had been instructed by the government to ramp up baggage checks as a result of the threat, with some luggage searches now being conducted as passengers queued to check in their bags.