Every year from Jan 01 to Mar 06 the redeye flight from SAN to IAD disappears. This is a planned UA route change. Where does this metal go during these 9 weeks. What is the required route that makes this particular route impossible to fly.

I fly SAN to IAD weekly and it is ALWAYS full. So this is not a late winter passenger capacity on the route issue.

Basically during these 9 weeks I am required to fly SAN-EWR-IAD. Yuck.