The Navy said Friday an aircrew in the Pacific Northwest was responsible for creating lewd skydrawings.
The incident comes amid raised awareness about sexual harassment in the workplace and even assaults.
" The American people rightfully expect that those who wear the Wings of Gold exhibit a level of maturity commensurate with the missions and aircraft with which they've been entrusted," the Navy said, in a statement provided to CNBC.
"Naval aviation continually strives to foster an environment of dignity and respect. 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," the statement read.
"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," it added.
The event happened Thursday when an EA-18G Growler attack jet (a variant of the F/A-18) flew in the skies above Okanogan, a community about 200 miles northeast of Seattle. The plane's flying pattern "left a condensed air trail resembling an obscene image to observers on the ground," the Navy spokesperson said.
The Navy promised a full investigation into the matter and possible action against the crew involved. The EA-18 aircraft involved was home-based at Naval Air Station Whidbey Island, Washington.
"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," Michael Welding, the base public affairs officer, said in a statement.
Social media was filled with reports discussing the incident and photographs showing the phallic sky images.
Separately, the Pentagon on Friday released data about sexual assaults at local installations, and it revealed the prevalence rates for men and women have gone down since 2012.
The prevalence rates of sexual assaults showed a decrease from 6.1 percent of active-duty women in 2012 to 4.3 percent in 2016, the most recent period with available data. For active-duty men, the prevalence of sexual assault went from 1.2 percent in 2012 to 0.6 percent in 2016.