Australia’s air traffic control agency is relying on hundreds of hours of overtime as it struggles to fill shifts in airport towers, a union analysis of internal rostering documents shows.

The staff union representing the nation’s air traffic controllers, Civil Air, has warned that understaffing problems at Airservices Australia are so severe they threaten to undermine its ability to provide air traffic services.

“The consequences ultimately are a reduction of air service provision, which could mean airspace closures, potentially, or a restriction of services or hours,” Peter McGuane, the union’s executive secretary, said. “The potential for that to happen is quite real.”

The claim has been strongly denied by Airservices, which says there is no shortage of air traffic controllers. It says there have been no airspace closures and no reduction in its ability to manage airspace safely and efficiently.

The organisation said it had more than 900 air traffic controllers, with another 65 in training, and requires about 800 to fully staff the air traffic management system.

“Like most industries, we are experiencing the impacts of Covid-19 and one of the worst flu seasons seen in years, leading to high levels of short-notice, unplanned absences of our staff,” an Airservices spokesperson said. “We are managing these short-term, unplanned absences safely through overtime shifts, governed by our Fatigue Risk Management System.”

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Last week, Airservices brought on a new service for air traffic in and out of Rockhampton and Mackay airports.

A union analysis of rosters for that service, seen by the Guardian, shows the scale of the overtime.

Operational shifts remain vacant for almost every day of June and all of July. Each day has at least one operational shift vacant. Some days have as many as five, according to the analysis.

The shifts are being covered by a huge increase in overtime. Civil Air estimates that Cairns control tower relied on 155 overtime hours in nine days from 10-19 June alone.

Overtime has exceeded 100 hours in the same nine-day period at Fraser, Monaro, Brisbane, Melbourne and Canberra, while Sydney recorded more than 500 hours, the data suggests.

Civil Air said last year’s announcement of a new retirement incentive scheme, which encouraged more than 100 controllers to accept generous packages, had compounded the problem.

That had exacerbated staffing pressures caused by Covid and the flu season.

“Those remaining have to fill the gaps, and while we’re pleased that members have been recognised for long careers and have been given an incentive to leave, it places an obligation on those who are remaining to work overtime to cover those vacant shifts,” McGuane said. “That impacts on their work-life balance.”

He said understaffing could ultimately create a “safety risk”.

Airservices strongly denied any suggestion that safety had been compromised.

It said the retirement incentive scheme had not “impacted our capacity to safely manage Australia’s air traffic management system”.

The scheme had been enacted during Covid, a time of reduced air travel, to reduce the impact of departing staff, Airservices said. Training of new controllers had been stepped up in parallel, it said.

Airservices said the new approach service for Rockhampton and Mackay was not understaffed.

“The service has been over-rostered while we establish demand and is not compromised by staff availability.”

Source: The Guardian