The US Navy has confirmed one of their jets was involved in the drawing of a penis in skies over Okanogan County in Washington state.
An official from Naval Air Station (NAS) Whidbey Island acknowledged a Navy E/A-18 Growler warplane was responsible for the "immature act" on Friday.
The aircrew have been grounded while an investigation is carried out.
Vice Admiral Mike Shoemaker, the commander of Naval Air Forces, told: "The Navy holds its aircrew to the highest standards and we find this absolutely unacceptable, of zero training value and we are holding the crew accountable.
"Sophomoric and immature antics of a sexual nature have no place in Naval aviation today. We will investigate this incident to get all the facts and act accordingly.
"This event clearly stands in stark contrast to the way our aviators and sailors are performing with utmost professionalism, discipline and excellence from our carrier flight decks and expeditionary airfields around the world today."
A television station reported that a mother in Okanogan County was concerned she might have to explain the phallic symbol to her young children.
There were others who appeared amused by the stunt.
Resident Ramone Duran told the Spokesman Review: "After it made circles at the bottom, I knew what it was and started laughing.
"It was pretty funny to see that."
Another onlooker tweeted that it was "the most monumental thing to happen" in their community.