You'd think being a pilot would be bloody exciting, soaring through the sky, being in control, but no, apparently, it can get pretty tedious - at least, according to one pilot who ended up using his time in the air to write 'I'm bored' and add a couple of dicks.

Pine Pienaar, director of Flight Training Adelaide, told Adelaide Now: "Young instructors, what can you do?" Before adding that neither he nor the company condoned the unnamed pilot's actions.

The cheeky in-air message was only visible to those who were monitoring his live-progress - so no harm done.

"We have grounded the aircrew and are conducting a thorough investigation - and we will hold those responsible accountable for their actions.

"The Navy apologises for this irresponsible and immature act."

An official statement from the US Navy read: "We find this absolutely unacceptable, of zero training value and we are holding the crew accountable."

Despite the threat of harsh punishment, a second military air crew were also investigated for using their aircraft to make a rude symbol.

A team from the Marine Corps were flying over southern California when they decided to use their flight path to draw a huge penis in the sky.

Experts say that it would have been very unlikely for anyone to see the shape from the ground - as the plane's propeller wouldn't have left trails in the sky during the specific atmospheric conditions that day.

But that wasn't enough for the US Marine Corps, with Major Josef Patterson announcing that an investigation had been launched.

"We've opened an investigation that is under way as we speak," he said.

Cocks.