On March 12, many moons rose near the Australian city of Darwin.

If you think it was a once-in-a-lifetime celestial happening, you are mistaken.

Hundreds of young and old flashers had turned up by the tracks at Livingstone, about 40km south-east of Darwin, on a cloudy day to bare their behinds at a train called The Ghan.

The flashers included some children who were not born when the first mooning happened, and babies who had their buttocks bared by their parents.

It was a unique way of greeting the train that was arriving in Darwin in the Northern Territories from the southern city of Adelaide, a 2,978km journey that can take up to 53 hours including tourist stops.

The train’s name is an abbreviation of its original moniker The Afghan Express – so named in tribute to the Afghan camel drivers who helped build the first stretches of the line in the 19th century.

The posterior-flashing practice first took place in February 2004, and then again 10 years later. It started as a good-natured gesture to welcome the train’s first run, according to locals.

“We have dinner parties on car trailers and silly things like that. And (someone) said, ‘We should moon the Ghan when it comes through,’” an unofficial local representative, Ms Michelle Salmon, told NT News in 2014.

Other flashers on March 12 were from a group calling itself the Noonamah Moonies, comprising locals who were part of the original mooners in 2004 and had returned for the now once-a-decade ritual while repeating the mantra to “get your backside trackside”.

For the mooning’s 20th anniversary, signs and posters inviting people to join the party “Mooning the Ghan” were placed near the train tracks.

Gallivanting locals showed up with beers in hand, ready to catch what some dubbed “full moon fever”.

“It’s not a bad day to flash your bum,” one mooner told Australia’s ABC News.

As the train approached the Livingstone Airstrip, horns blaring, the flashers lined up disorderly and dropped their pants for what appeared to be the 20-odd seconds it took for Australia’s longest passenger train to drive past them.

Former Australian prime minister John Howard was on board the first Ghan train in 2004, after the line was extended from Alice Springs to facilitate travel and freight transport from coast to coast.

It is not clear if he witnessed the buttocks lining up to greet the train.