The sky above Darwin rumbled, roared and shook.

For the past two weeks, fighter pilots from all corners of the globe have gone head to head in screaming jets during mock battles.

Up to 3000 service men and women from 10 nations - including Australia, the US, Singapore, Malaysia and France - have catapulted into action from RAAF bases in Darwin and Tindal, near Katherine.

This may explain why some NT residents reported they were seeing UFOs.

Testing some of the most high-tech aircraft in the world, such as F/A-18s, F-111s, F-16s and E3 AWACs, personnel were divided into red and blue forces.'

The multinational training exercise known as Pitch Black also included NATO forces and live bombing at the Delamere Weapons Range in the outback.

Wrapping up the exercise today, Acting Exercise Director Group Captain Alan Clements said the "war" - waged day and night - had been two years in the planning.

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"It's essential that our aircrews are able to operate safely and effectively both day and night in the defence of Australia, and Pitch Black is vital to enable us to practise and refine those skills," he said.

And while the fighting was pretend, the desire to win wasn't.

"The intensity of activity tested everyone connected with the exercise, as it would if this was a serious confrontation," said Group Captain Clements.

"The aircrew honed vital skills, the aircraft maintainers worked day and night to ensure their planes were ready to go, commanders and planning staff were continually devising tactics to ensure activity.

"One of the main purposes of this exercise was to test the interoperability of the Royal Australian Air Force with air forces from other countries."

Group Captain Clements also thanked Territorians for their forbearance.

"Without your generous support this exercise wouldn't have been the success it turned out to be," he said, adding the next time they will have to suffer booming heavens won't be until 2010.