There is a classic line from the movie Die Harder when an air traffic controller tells his colleagues to "stack 'em, pack 'em and rack 'em" meaning to keep approaching aeroplanes in a holding position while they deal with a "code red" emergency.
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It's Hollywood overkill but still not a 100 per cent removed from the reality of what happened on Wednesday as Sydney, Canberra and other airports along the eastern seaboard dealt with the massive storm that hit Sydney.
And instrumental in managing the storm-induced chaos that hit the airports was the Commonwealth organisation Airservices Australia in Canberra, particularly its national operations centre which works from a nondescript building on Constitution Avenue.
Airservices Australia manages 11 per cent of the world's airspace. It has 29 towers and 1000 air traffic controllers around the country, with Melbourne and Brisbane the two major centres handling most of the airspace. Last year it managed the movement of 4.5 million flights carrying 90 million passengers.
The network is coordinated from the national operations centre in Canberra, with 15 to 20 staff trying to smooth the passage of about 11,500 flights a day – working to "minimise the risk of collisions, while allowing the maximum number of aircraft to fly safely in our skies".
Airservices Australia executive general manager air traffic control Greg Hood said the centre's role included speaking each day with the airlines to see how the weather and other factors might affect each runway's capacity at any hour of the day and whether flights could be delayed or cancelled to account for the changing factors.
"We do all the pre-tactical planning for air traffic control from here but of course things go wrong, flights are delayed, we have aircraft emergencies, we have bad weather and that's when the people in the field take over and they manage the situation tactically," Mr Hood said.
And that's what happened on Wednesday as the air traffic controllers on the ground came to the fore.
Mr Hood said the weather was so severe at Sydney airport on Wednesday as three different storms lashed the city that aircraft were electing not to land and instead enter "outer holding stacks" about 150 kilometres north of Sydney and 150 kilometres to the south-west.
"I don't know if you've seen Die Harder but it was 'rack 'em and stack 'em'," Mr Hood said.
"But of course we take safety so seriously what we don't want is to keep filling up the holding stacks and having dozens of aircraft holding.
"[On Wednesday] because the thunderstorms kept coming through we actually implemented what we call a 'ground stop' and said, 'No more [aircraft]. No more out of Brisbane, no more out of northern ports, no more out of Melbourne until we clear the backlog out of the holding patterns so we don't overload the air traffic controllers'."
Mr Hood said there were about 1000 flights planned in and out of Sydney on Wednesday – a typical day – and the storm saw 116 flight cancellations and 14 diversions – nine domestic and five international.
The flights were diverted to airports including Coffs Harbour, Brisbane, Williamtown and Canberra, where a Cebu Pacific A330 airbus bound for Sydney from Manila landed.
"You had aircraft departing and aircraft descending and also moving left and right of the storm cells, so it was quite challenging," Mr Hood said.
"But I'm pleased to say all the feedback I received was positive. We really do have the best air traffic controllers in the world and they certainly performed well [on Wednesday]."
