Pilots conducting an engine endurance test on a Boeing 787-8 Dreamliner injected some levity into an otherwise boring 17-hour loop around the continental United States.

The flight took off from Seattle and flew about 3,200 kilometres to Marquette, Mich., banked southwest towards Kansas before zagging into a seemingly random exploration of the airspace above Kentucky, Tennessee, Alabama, Mississippi, and several other states before landing again in Seattle. Pretty exciting stuff, right?

Had the flight been hijacked by a band travelling of Etch A Sketch enthusiasts? Were the pilots amusing themselves by wasting pricy jet fuel?

It took a while for aviation enthusiasts following Thursday’s flight on tracking sites like FlightAware and Flighradar24 to realize what the cheeky aviators were up to.

Flight BOE004 was, in fact, tracing the shape of the mid-size, wide-body, twin-engine jetliner across the sky -- wings, fuselage, tail fins, engine and all.

Nose to tail, the massive outline stretched from Wyoming to somewhere in Alabama. The wingspan touched Michigan at one end, and Texas, not far from the U.S. border with Mexico, at the other.

This is not the first time Boeing test pilots have used the sky as a massive canvas. A 787 traced Boeing’s logo in 2012, and earlier this year one of the company’s 737 MAX spelled out “MAX” on a 9-hour flight.

In 2011, Boeing pilots used a 4,000-kilometre test flight as an excuse to pick up “fry-and-slaw-filled sandwiches” in Pittsburgh, according to Tribelive.com.

While Boeing has stood by its pilots’ creativity in the past, a number of social media users chided the aviation giant for wasting fuel and causing undue harm to the environment.

By one estimate, the 787-8’s nearly 18-hour flight dumped more than 300,000 kg of carbon dioxide into the atmosphere.

“Wow. Very useful,” remarked one snarky Twitter user. “Nice but don't u think that it's a waste of fuel? U can test it out in a lab with weights to simulate the passengers,” said another commenter.

Flighttrader24 stepped in to help clear things up, writing “Boeing is performing an endurance flight test for a new engine that will power the 787-10” and “Sometimes flight conditions are necessary for tests.”

Other commenters could not help themselves from reminiscing about other memorable times aircraft left eye-catching shapes in the sky. Some of them less related to aviation.