The two pilots, who have not been identified, have not flown since the start of the investigation, Maj. Josef Patterson, a spokesman for the Miramar, California-based 3rd Marine Aircraft Wing, told Military.com.
The news of the grounding was first reported Tuesday by the Washington Examiner.
"Although not flying for the time being, the two Marine Corps aviators are still providing vital squadron ground support functions," Patterson said in a statement. "Disciplinary or administrative action, if any, will be determined following the completion of the investigation."
The unusual flight pattern made the news Oct. 23 when it was highlighted by the Twitter account Aircraft Spots.
Somebody needs to have a word with the crew of US Navy T-34C 160937 SHUTR91 out of MCAS Miramar 😂😂 pic.twitter.com/WgrgkKzRln— Aircraft Spots (@AircraftSpots) October 23, 2018
Marine Corps officials quickly acknowledged that it was crew members with Marine Fighter Attack Training Squadron 101, out of Miramar, who had flown the T-34C Turbo Mentor trainer aircraft in the offending pattern while passing over a saline lake outside of San Diego.
"The aircrew's chain of command are committed to maintaining an environment of professionalism, dignity and respect," Patterson said in a statement at the time. "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."
The incident gained more attention because it came on the heels of a 2017 incident in which two Navy aviators out of Naval Air Station Whidbey Island, Washington, used an EA-18G Growler to skywrite a crude image of male genitalia that was visible from the ground. The two pilots were ultimately disciplined, but allowed to keep their aviators' wings.
In this case, there was no skywriting, and the Marine aviators might reasonably have thought their apparent prank would pass unnoticed.
Patterson told Military.com he could not speak for the investigating officer as to whether the lack of visibility might affect the outcome for the two pilots.
"I will say, you couldn't see it from the ground. I'm assuming that's part of it," he said. "What it doesn't change is that it happened."