The runway was understaffed and unable to keep up with the volume of flights

About 26 outbound flights had to be cancelled and three flights were delayed

It was the middle weekend of school holidays in NSW and the final one for VIC

Thousands of fliers have had their journeys interrupted by an airport staff member who called in sick the day before students were due back at school.

An air traffic controller rang it in at Sydney Airport on Sunday, leaving the runway understaffed and unable to keep up with the high volume of flights.

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About 26 outbound flights had to be cancelled from airlines including Qantas, Qantas Link, Tiger Air, Jetstar and Virgin passengers, Daily Telegraph reported.

Thousands of fliers have had their journeys interrupted by an airport staff member who called in sick the day before students were due back at school (stock photo)

The damage spread to regional airports where many planes didn't arrive due to being cancelled out of Sydney, causing chaos for those with connecting flights.

An additional three flights were delayed because of the employee's sick day.

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Flight schedules for the entire day had to be re-organised due to the airport being down a staffer, according to Airservices Australia

By the afternoon, schedules had returned to normal and flights that were due for Sydney later in the day were expected to arrive on time.

The damage spread to regional airports where many planes didn't arrive due to being cancelled out of Sydney, causing chaos for those with connecting flights (stock photo)

Disappointed commuters took to Twitter to air their frustrations, some accusing their airline of inadequate communication.

'First Jetstar cancel my 7am flight on Friday to Sydney without notifying me and then our flight at 4pm today to go back to Melbourne is cancelled with no notification. What a waste of money and points,' one traveler wrote.

'The reason our Qantas flight was cancelled this evening was because there aren't enough air traffic controllers. Is this a normal thing?,' a puzzled flier tweeted.

More flights were scheduled because it was the middle weekend of school holidays in New South Wales and the last weekend of break for Victorian students.

Disappointed commuters took to Twitter to air their frustrations, some accusing their airline of inadequate communication (stock photo)

Airlines reportedly put passengers on later flights or delayed them to board a separate flight on Monday to cope with the backlog.

A statement from Qantas said it was doing everything it could to 'get customers moving', 'but the reduced take off and landing rates meant we've had to cancel some flights.'

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'Some customers were moved to flights on Sunday evening but as it's school holidays we have limited spare seats so others won't travel until Monday.'