Greece's transport ministry said on Wednesday that its civil aviation chief had quit over the embarrassing January 4 airspace blackout that snarled flights for hours.

The move came hours after an official report into the incident blamed the glitch on "obsolete technology" at Athens International Airport, one of the world's top travel destinations.

According to the Civil Aviation Authority (YPA), the malfunction began at 8.59am (0659 GMT) on January 4 when multiple radio frequencies serving Athens airspace were hit by continuous "noise" interference.

The agency's transmitters began sending out "involuntary signal emissions", YPA said.

Hundreds of flights had to be diverted to neighbouring countries, with thousands of travellers hit. YPA said at the time that the problem was "unprecedented".

No signs of a cyberattack or intentional sabotage were detected, it added.

An infrastructure overhaul costing US$350 million is currently underway, which includes digital transmitters that will be delivered this year. Greece's junior transport minister admitted last week that the airport's communications systems should have been upgraded "decades" earlier.

"These are systems we know are outdated," Konstantinos Kyranakis said.

Last month, the European Commission referred Greece to the EU Court of Justice for failing to put in place measures to design and publish performance-based navigation (PBN) procedures at Greek airports that should have been in place five years ago.

Athens International Airport handled nearly 34 million passengers last year, an increase of 6.7 percent over the previous year. (AFP)