One flight recently, I had an interesting exchange with Jacksonville Approach, south of Jacksonville at 9000 feet.
Approach: “N1234, be advised traffic 11 o’clock 10 miles at 9500 can exhibit abrupt changes in altitude and position.”
Me: “Will observe. That a military aircraft?”
Approach: “I’m not really allowed to say. Just watch out.”
That’s a new one for me! I wonder what was being tested in the skies that day.
Raleigh, North Carolina