Back in 1999, word went out that a Learjet had ascended to veered off course from its intended flight path and was cruising across the United States. This caused a lot of concern after crews remained unresponsive to any attempts at communication. Left with little alternative the United States Air Force dispatched an F-16 to intercept the Rogue Learjet
The F-16 made a swift departure and eventually caught up with the Learjet and conducted an inspection. The private jet was flying at a much higher altitude than normal causing the windows to form ice and it made an inspection of the interior difficult for the F-16 pilot. However, the plane appeared to be flying normally despite lack of response.
There was little else the F-16 could do except monitor the situation as the Learjet neared the end of its fuel reserves. The key reason that no action was taken against the Learjet is that attacking it could potentially cause its debris to harm innocents on the ground. It eventually crashed over in a hayfield over South Dakota and the was learned that a loss in cabin pressure caused the crew to lose consciousness.
The incident is retold in this video clip from the Smithsonian Channel.