Ghost planes occur when the crew and passengers are incapacitated (often cabin depressurization and often dead) midflight. The plane continues on autopilot and crashes when it runs out of fuel.

If the grounds crews can’t get hold of the plane, fighter jets are sent up to assess the situation. They look through the windows to see if there is life. Ice inside the windshield also indicates a loss of pressure. Then they sill have to let it crash.