On Tuesday, the United States Marine Corps announced that it would be launching an investigation into reports that a Marine Corps aircraft deviated from its projected flight path to draw an obscene image in the skies over Southern California that could only be seen via flight tracking software.

The unusual flight, first spotted by Aircraft Spots, a Twitter account devoted to tracking military flights, shows a T-34C single-prop training aircraft drawing what seems to be a penis shape over California’s Salton Sea. The trainer plane, which is reportedly part of Marine Fighter Attack Training Squadron 101 out of Miramar, likely appeared to be executing a common holding pattern over the waterway for any bystanders on the ground. It was only when viewing a rendering of the aircraft’s flight path that one could see the pilot’s artistic rendering.

The internet seemed overwhelmingly entertained by the spectacle, but, as one might expect, the Marine Corps wasn’t quite so enthused.

“A T-34C aircraft assigned to Marine Fighter Attack Training Squadron 101, 3rd Marine Aircraft Wing, flew an irregular flight pattern over the Salton Sea that resembled a phallic image,” an official 3rd MAW release said. “An investigation to uncover the facts and circumstances surrounding the incident is ongoing. The aircrew’s chain of command are committed to maintaining an environment of professionalism, dignity and respect. The Marines and Sailors of 3rd Marine Aircraft Wing will perform at the highest levels expected of professional war fighters, and uphold our core values of honor, courage and commitment.”

While this particular incident has caught the attention of social media, likely in no small part because it was discovered through social media, this is far from the first time U.S. military aviators have taken to drawing penises in the sky. In fact, in recent years, it’s become a bit of a trend.

In November of last year, a U.S. Navy crew aboard an EA-18G Growler used their jet’s contrails to sketch out a giant phallus in the skies above Washington State. Unlike the recent Marine Corps incident, the penis in the sky was readily apparent to anyone beneath it, and social media was promptly flooded with photos from Washington residents who couldn’t help but notice that the sky above them was beginning to resemble a desk in high school detention.

“When they came down, the aviators were apologetic,” said Navy spokesman Cmdr. Ron Flanders. “The aviators admitted that they had done it after it occurred. When they appeared before the (Field Naval Aviator Evaluation Board) they were contrite. They realized that this was an embarrassment to Naval Aviation and the entire Navy. This sort of conduct is contrary to the core values of the Navy.”

Neither of the pilots were identified by the Navy, though the branch did disclose that one of the two pilots soon transferred out of Naval Air Station Whidbey Island to Naval Air Station Meridian in Mississippi — where he began serving as a flight instructor.

In April of this year, the U.S. Air Force decided to get in on the action as well, but instead of drawing a penis in the skies over the United States, Rhineland-Palatinate, Germany became the backdrop for what was, admittedly, the least artistically rendered penis of the bunch.

Each of these branches, of course, has issued repeated statements regarding the lack of professionalism on display in each of these occurrences; though no publicly acknowledged punishments have been very severe. It seems likely, then, that while unprofessional, the U.S. military truly sees these incidents as inappropriate, sure, but mostly harmless.

The real question now seems to be, with the Marine Corps, the Navy, and the Air Force all drawing penises in the sky… how long will it be before we see an Army flight drawing similar headlines?

Because as far as inter-branch rivalries go, it would certainly seem that the gauntlet has been thrown.