All commercial and civilian aircraft in New Zealand were temporarily grounded on Tuesday when a fault crippled the nation's air traffic control system, causing long delays and some cancellations.
Airways New Zealand, which manages air traffic control in the South Pacific country, said all flights, including international and domestic services, were affected.
The government agency insisted no planes or passengers were in danger during the outage, which lasted more than two hours and left air traffic controllers without any radar.
As a result, all flights were banned from taking off and those already in the air were guided down using "visual manual separation" -- using eyesight and radio contact -- the Civil Aviation Authority (CAA) said.
Airways NZ blamed the problem on "an internal network failure".
"Airways immediately suspended all flights while we investigated the issue and until we could be satisfied that we could operate safely," it said.
"We have now identified the issue and thoroughly tested the integrity of the system."
Transport Minister Simon Bridges said air traffic controllers communicated with flights via radio during the radar outage, also stressing there was "absolutely no compromise to the safety of passengers or planes."
But the CAA said it was concerned about the incident and had launched a safety investigation.
A CAA spokesman said he was unaware of any similar failures in the past and it was being treated seriously.
"We'll certainly be very keen to find out exactly what happened," he told AFP.
Asked whether such a scare was unacceptable to the travelling public, he responded: "Absolutely".
Local media reported close to 200 flights were affected, with long delays and some cancellations at airports around the country.
Passenger Paul Le Comte was awaiting take-off at Christchurch airport when the ban was imposed and said he and his fellow passengers experienced a number of false starts before finally departing.
"Looks like Airways NZ has found the extension cord for the radar that the cleaning lady kicked out. We are taking off soon baby. Thanks," he joked on Twitter.
Anna Smith told Radio New Zealand she was trying to travel from Wellington to Hawke's Bay for a funeral.
"We don't have many options at the moment... until we get to the front of the queue we won't really know what's happening," she said.
Air New Zealand said 160 of its flights were affected and it would take time for the backlog to clear.
Auckland airport, the country's largest, warned travellers to expect delays, while Christchurch airport advised them to contact airlines for flight information.
Salis Elias told TVNZ said he concerned at the reason for his plane's delayed departure from Auckland but was making the most of the situation.
"How do planes in the sky land without radar?" he asked. "Like all good Kiwis in a crisis, we're heading to the pub to make contingency plans."
Airways NZ's website says it manages 30 million square kilometres (nearly 12 million square miles) of airspace, handling about one million aircraft movements annually.
"Airways NZ apologises to all passengers who have been affected by this outage," it said in a statement.