I'm a First Officer for TMC Airlines, a small freight airline operating Lockheed Electras based at Willow Run Airport in Detroit, Michigan. We use the call sign Willow Run Three Forty-Six, and we'd just picked up a load of freight at Muskegon, Michigan and were en route to Oakland, California. The time was about 07007. As we reached our final cruising altitude of FL220 at the west side of Lake Michigan, we got this message from Chicago Center:
"Willow Run Three Forty-Six, descend and maintain 6,000."
After exchanging looks of amazement with my captain, I replied:
"Chicago, ah if you really need us at 6,000 we'll start down. But it's way early for our descent into Oakland, California."