Unscheduled flight

On June 12, 1977, an unscheduled flight, Flight 990, was picked up by radar as it approached a private airstrip in Arizona. There was no flight plan, no pilot ID, and no takeoff record. But the landing was genuine. The jet touched down without a hitch. The cabin was pressurized. The lights were still on. No crew, no passengers. Not even luggage. Then came the radio calls. Three hours after landing, air traffic control recorded 43 transmissions. Air traffic control recorded 43 transmissions from the jet's onboard system. The voice kept saying, "This is Flight 990, which we were not supposed to go. Please let us come back." It wasn't just voice logs, the plane responded to commands. When asked to identify itself, it said: "We boarded with names. Now we are just echoes." The Department of Transportation moved the plane to a concrete bunker.  They later redacted all records of its existence. In 2021, a hobbyist radio scanner picked up the sound again. Same frequency, same text.

Mysteries continue.