A mysterious fleet of drones entered restricted airspace and swarmed a U.S. military base along the Virginia coast for 17 days late last year, stumping the Pentagon, according to a new report. 

For several nights last December, U.S. military personnel reported witnessing a fleet of unknown unmanned aircraft breach restricted airspace over a stretch of land at Langley Air Force Base along Virginia's shore, the Wall Street Journal first reported. 

The drones would start to arrive about 45 minutes to an hour after sunset each night, one official reportedly told U.S. Air Force Gen. Mark Kelly, who joined several other officers responsible for the country's most advanced jet fighters, including F-22 Raptors, on a squadron rooftop. 

Kelly described the first drone he saw as roughly 20 feet long and flying at more than 100 miles an hour, at an altitude of roughly 3,000 to 4,000 feet. As many as a dozen or more drones followed, flying across Chesapeake Bay, and then traveling toward Norfolk, Virginia, and through a space overlooking the base for the Navy’s SEAL Team Six and Naval Station Norfolk, the world’s largest naval port, according to the Journal. 

BUTTIGIEG'S MESSAGE ON RESTRICTING CIVILIAN DRONES NEAR HURRICANE HELENE DAMAGE PROMPTS OUTCRY, CLARIFICATION

Pentagon aerial view

Aerial view of the Pentagon in Arlington, Virginia, on March 31, 2024. (Daniel Slim/AFP via Getty Images)

The report said officials could not determine if hobbyists or adversaries – such as China or Russia – were responsible for the drone fleet. Reports of the matter reached President Biden and resulted in two weeks of meetings at the White House in December 2023, the Journal reported. Those meetings included the Defense Department, the FBI and the Pentagon’s UFO office, as well as outside experts. 

MILITARY SENDS RESOURCES TO FLORIDA IN WAKE OF HURRICANE MILTON WHILE HELENE RECOVERY EFFORTS CONTINUE

Pentagon briefing room

A press conference at the Pentagon on Aug. 20, 2024. (Celal Gunes/Anadolu via Getty Images)

Fox News Digital reached out to the White House and Department of Defense for comment. The DoD referred Fox News Digital to Langley Air Force Base for more information, but they did not immediately respond to an inquiry. Neither did the White House.

Two months before the drone fleet emerged in Virginia, five mysterious drones reportedly breached restricted airspace over a government nuclear weapons experiment site in Nevada. 

CLICK HERE TO GET THE FOX NEWS APP

Four of the drones were detected by the Energy Department’s Nevada National Security Site outside Las Vegas, while the fifth was spotted by employees, according to the Journal. The facility has reportedly since upgraded its detection system, but officials have not determined who was behind the breach.