An international pilots group says maintenance of the Auckland Airport runway has not kept up with the rate that it's deteriorating.
A number of international and regional flights were diverted yesterday afternoon after the runway was shut down for maintenance.
The International Federation of Air Line Pilots' Associations said in a statement that the runway has been degrading over the past few years and as a result, there have been 15 short notice unplanned runway closures.
"One, on 24 January 2020, resulted in the runway being closed for 40 minutes and causing the diversion of 9 aircraft, including a wide body international arrival," the statement said.
The association said it's concerning that the airport has only one runway, increasing risk of debris and more frequency of closures.
"With the increasing occurrences of damage to the runway there has been an increased risk of foreign object debris (FOD) damage. Some pieces of broken concrete have been reported up to 30cm by 30cm and 12cm thick," it said.
It said the airport management are planning large scale work for the runway, including replacement of the concrete slabs near some touchdown zones, but the work will not begin until later this year and "will take months to complete".
Captain Andrew Ridling from the New Zealand Airline Pilots' Association said he'd been aware that the runway's been deteriorating for a number of years, and he thought repairs were well underway.
But he said it was clear that things were getting worse, to the point he was wondering whether adequate investment had been made in the runway.
"There's around 280 slabs of concrete on the northern end of what we call Runway 23 in Auckland. These were reconstructed in 1992 and they're reaching the end of their design life, from what I understand so need some urgent maintenance," he said.
"From what I'm hearing from people, they're breaking down."
Mr Ridling said the degradation was occurring on the most heavily used part of the runway, with some 80 per cent of in-bound flights landing there.
"For me the shock came when I heard that 30cm by 30cm - which is a foot by a foot - blocks of concrete breaking off and being picked up off the runway. You know, it only needs to occur once to become a pretty major safety concern."
Mr Ridling said the cost of the disruptions to airlines will be starting to mount.
"I would suggest that every aircraft carrying an extra 20 to 30 minutes of fuel would get into the millions. We're not talking small beers here."
The Auckland Airport said in a statement that it will carry out an immediate review following yesterday's closure of the runway.
It's the second time the runway has been temporarily closed for maintenance this year, but the airport says the closures were unrelated.
"The last thing we want is for people's travel plans to be disrupted, but safety is our top priority and we have no tolerance for debris or defects which may compromise this," it said.
"While the two recent closures were unrelated, Auckland Airport recognises they have occurred in close succession with an impact on travellers and our airline partners."
The airport said there's a current maintenance programme, but it will assess whether it needs to be changed.
"The review will be completed over the next three weeks," it said.