But Reuters reports that Australian authorities said a US Navy P-8 Poseidon, the most advanced search aircraft in the world, had been unable to find the objects.

"A US Navy P-8 Poseidon aircraft was tasked to investigate reported object sightings by the Chinese aircraft made at 33,000ft," an AMSA spokeswoman said in an emailed response to Reuters.

"The objects were spotted by the Chinese aircraft as it was heading back to Perth. Drift modelling was undertaken on the sighting. The P-8 was unable to relocate the reported objects."