An Adelaide pilot has taken workplace venting to new heights by etching "I'm bored" into the sky.

Key points: Radar picks up an Adelaide pilot writing "I'm bored" in his flight path

Radar picks up an Adelaide pilot writing "I'm bored" in his flight path Former Qantas pilot says it was a "harmless pursuit"

Former Qantas pilot says it was a "harmless pursuit" Pilots around the world have etched their artwork into their flight paths

The Diamond Star plane, operated by Flight Training Adelaide, spent a little over three hours in the air on Tuesday to draw the letters over South Australia.

The message was not seen by people on the ground, but was visible to aviation followers watching live flight tracking programs and websites.

It is believed the pilot, who was working out of Parafield Airport, north of Adelaide, was "running in" a new engine.

The FlightAware website captured the pilot's work between 8:53am to 11:57am.

The pilot flew several loops, creating some somewhat explicit graffiti along the coast, before tracing "I'm bored" over the Princes Highway.

Retired Qantas A380 pilot Chris Wilson said he thought the message was "harmless".

"It's not very common for someone to do this. It's the first one I've seen," Mr Wilson said.

"I think it's a harmless pursuit. He obviously is bored.

"I'd say he was a young pilot trying to build up some hours."

Mr Wilson said the pilot would have been following the GPS path.

"I would think it's quite safe, providing they're following all the normal flight rules," he said.

Civil Aviation Safety Authority spokesman Peter Gibson said pilots drawing pictures was "uncommon but not unheard of".

"All pilots plan a track for their aircraft to get between where they're going from and to — now what that track looks like once it shows up on radar of course is another thing entirely," he said.

"As long as the pilot flies the aircraft safely and complies with all the aviation safety rules we are not too concerned about what that track looks like."

Flight Training Adelaide has been contacted for comment.

Pilots get creative around the world

A private aircraft flies in the shape of a plane over Germany. ( Supplied: flightradar24 )

The "bored" artist is not the only pilot creating messages or artwork, according to the Flightradar24 website.

Throughout the world pilots are drawing planes, love hearts, leaving messages and even signing their own work on return flights.

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According to overseas media reports two US Marines were grounded over a stunt where they created a "sky penis" over California in October 2017.

A month later, an Airbus pilot during a test flight produced a clear image of a Christmas tree complete with baubles over Germany.

The tree, according to the BBC, was rendered in several colours on Flightradar24 website to show the plane's varying altitudes.

The phenomenon has drawn comparisons with runners and cyclists using tracking app Strava to overlay street maps with detailed drawings.

In one instance, a Perth cycling group traced the path of a goat onto the city's streets.

Weeks later, they followed up that feat with an image of the state's emblem, a numbat.

Cycling group member Ben Jones told ABC Radio Perth they mapped out the route first to get the image right.

The numbat ride covered 192.2 kilometres and took six hours and 33 minutes to complete.

"I was a little bit disappointed with some of the detail … I think numbats have a mask over their eyes which I couldn't get, but it's good enough to know what it is," Mr Jones said of the completed map.

"All the people who told us last year that we had to do something again are impressed, which is good.