Lost: One F-35 fighter jet, somewhere over South Carolina. If found, please call the Marine Corps.

On Monday, an array of government and civilian agencies were still searching for a missing F-35, one day after a pilot on a training mission ejected and the military inexplicably lost track of the stealthy jet, which can reach supersonic speeds.

Joint Base Charleston even made an unusual plea for public help, releasing a phone number to call with any information about the lost F-35.

The search prompted widespread speculation. Was the jet still somehow airborne, perhaps flying on autopilot? Had it crashed undetected into a lake or the ocean? Does the Pentagon really have no method for tracing it?

“How in the hell do you lose an F-35?” Representative Nancy Mace, a South Carolina Republican and the first woman to graduate from the Citadel, asked her social media followers. “How is there not a tracking device and we’re asking the public to what, find a jet and turn it in?”

The mystery began when a Marine pilot used an emergency parachute to eject from the F-35B Lightning II on Sunday afternoon over North Charleston, S.C. He was taken to a local medical center and was in stable condition there, Jeremy Huggins, a spokesman for Joint Base Charleston, said Sunday.

It was unclear why the pilot needed to bail out. A second F-35 pilot who had also been on the training mission landed without any problems, Tech. Sgt. James Cason, another base spokesman, said.

On Monday afternoon, about 24 hours after the pilot ejected, Sargeant Cason said that the search for the F-35 was continuing.

“Clearly, as everyone can tell, it has not been located yet,” he said.

Based on the missing plane’s last known position, the base had been focusing on an area around Lake Moultrie, a large lake about 33 miles north of Charleston, and Lake Marion, the state’s largest lake, in coordination with the Federal Aviation Administration, Joint Base Charleston said.

The search involved the Marines, its Second Marine Aircraft Wing, Navy regional authorities in the Southeast, the Civil Air Patrol and the Federal Aviation Administration. Law enforcement teams across the state were also helping.

The disappearance prompted jokes and memes on the various social media sites.

On Threads, the Instagram platform, the actor Misha Collins wrote under a picture of the jet: “That’s what they get for leaving the keys in the ignition. In other news, check out my new listing on Craigslist. No lowball offers!”

“What’s the problem?” Tim Robinson, the editor in chief of Aerospace, the magazine of the Royal Aeronautical Society, asked on X (formerly Twitter). He posted a photo of an F-35 on a golf course. “I just sneaked off for a quick round of golf.”

More seriously, the missing jet prompted broader safety concerns.

The Marines released a statement on Monday saying that Gen. Eric M. Smith, the acting commander of the Marines, had directed all Marine Corps aviation units to conduct a two-day “pause in operations” this week to discuss aviation safety matters and best practices.

The statement said the directive came after three “Class-A aviation mishaps” over the last six weeks. Such mishaps involve property damage of $2.5 million or more, according to a Marine Corps document.

During the “safety stand down,” aviation commanders will lead discussions with Marines focusing on the fundamentals of safe flight operations, ground safety, maintenance and flight procedure and maintaining combat readiness, the statement said.

The F-35 is one of three types of small jets that have been made for the U.S. military.

The F-35B, which can both take off and land vertically as well as hover in place, is only operated by the Marine Corps, which can fly them from aircraft carriers and smaller amphibious assault ships alike.

The jet is designed to carry weapons like air-to-air missiles and guided bombs in internal bays, which reduces the warplane’s radar signature, making it harder for potential enemies to find. That stealthiness may also be partially responsible for why the Pentagon appears to have lost contact with the plane.

Manufactured by Lockheed Martin, the F-35B Lightning II completed its first combat strikes for the Marine Corps in Afghanistan in 2018.

The F-35’s Joint Strike Fighter program is the Department of Defense’s most expensive weapon system program, with estimates that it will cost nearly $1.7 trillion to buy, operate, and sustain the aircraft and systems over their lifetime, the Government Accountability Office said in a report released in May

The cost of the Marine Corps jet has varied over the life of the program. The federal government said it was as low as $70 million in 2012, and the Project on Government Oversight said it was as high as $135 million in 2020.

John Ismay and Christine Hauser contributed reporting.