Passengers at airports across Australia have been delayed due to a global outage of passenger screening systems, while a separate Jetstar IT issue has cancelled or delayed dozens of flights.
Sydney Airport has also been overwhelmed with smoke from bushfires ravaging NSW. The airport operated under low visibility conditions between 11am and 2pm on Tuesday, leading to delays up to 30 minutes. At one stage the airport's smoke alarm was triggered by smoke seeping into the terminal building.
On Tuesday morning an outage of the Advance Passenger Processing (APP) caused delays at international airports including Sydney, Brisbane and Auckland.
The APP is the system used to confirm whether a passenger has authority to depart or arrive and that they have the appropriate passport and visa.
A spokesman for Sydney Airport advised passengers to allow plenty of extra time due to the delays.
"International passenger check-ins are being delayed between approximately 30 and 60 minutes due to an outage in the processing system airlines use to check-in passengers," the spokesman said.
"Some airlines have intermittent access to the system, with others manually checking in passengers."
Meanwhile a separate IT problem affected budget airline Jetstar on Tuesday morning, causing 24 flights to be cancelled and more than 40 to be delayed.
The technology problem occurred between 5am and 10.30am and affected Jetstar's check-in facilities across the country. The issue has been resolved but thousands of passengers are affected as the airline deals with the backlog of delays and cancellations.
It comes at a critical time for Jetstar as hundreds of pilots and ground crew prepare to go on strike ahead of the busy Christmas period.
Pilots plan to walk off the job this weekend amid stalled wage negotiations, with the airline bracing for major disruptions to its flight network.
Meanwhile several large bushfires surrounding Sydney are causing havoc at Sydney Airport, with the smoke alarm triggered by the dense smoke blanketing the city.
Qantas passenger Imre Hegedus arrived at the airport mid-morning and said the smoke was very thick when the alarm went off.
"There appeared to be smoke inside the building and I thought that can't be right," Mr Hegedus said. "It's really hard to see planes a couple of hundred meters away."
"There was even smoke in the tunnel coming to the airport - it was crazy. [But] it's being managed as well as it possibility as it can be."
A spokesman for the Australian Border Force did not answer questions about the passenger processing system, referring Traveller to Sydney Airport instead.
A spokeswoman for SITA, the company behind the APP, said while the problem had been fixed SITA remains on "high alert" as it investigates what caused the outage.
"We regret any impact this incident has had on our customers and passenger," the spokeswoman said.