A live firing exercise by Chinese warships in the Tasman Sea went undetected by air traffic authorities for 30 minutes, with the alert coming from a Virgin pilot rather than government officials.

Military exercises conducted by three Chinese warships resulted in 49 aircraft being forced to change course in a busy area of airspace between Australia and New Zealand on Friday.

Airservices Australia officials told Senate estimates hearings on Monday a Virgin pilot alerted his agency after overhearing chatter from the ships while flying nearby.

‘It was in fact a Virgin Australia aircraft that advised one of our air traffic controllers that a foreign warship was broadcasting, that they were conducting live firing 300 nautical miles east of our coast,’ chief executive Rob Sharp said

‘So that’s how we first found out about the issue.’

The exercise took place in international waters and did not breach international law, but Anthony Albanese and Defence Minister Richard Marles both said China had not given sufficient notice. 

The Australian Navy would usually expect to have 12 to 24 hours’ notice of such an exercise. 

On Saturday, China performed a second live-firing exercise in the Tasman Sea, northeast of the Bass Strait, with New Zealand Defence personnel witnessing a Chinese warship firing its gun. 

Military exercises conducted by three Chinese warships in the Tasman Sea resulted in 49 aircraft being forced to change course between Australia and New Zealand on Friday 

And on Sunday, China accused Australia of ‘hyping up’ the live firing exercises in response to complaints of insufficient notice. 

Chinese defence ministry spokesperson Wu Qian said Australia’s description of the events was ‘completely inconsistent with the facts’.

‘China’s actions are in full compliance with international law and international practices and will not affect aviation flight safety,’ Ms Wu said in a statement.

‘Australia, knowing this well, made unreasonable accusations against China and deliberately hyped it up. We are deeply surprised and strongly dissatisfied with this.’

Some commentators have described the move by China as an aggressive demonstration of military power.