Jason Anderson was forced to withdraw from Moto 1 at Thunder Valley, and he will not be lining up for Moto 2 later today.
During the TV broadcast, Georgia Lindsay reported that Anderson is suffering from altitude sickness and will immediately fly home to recover.
Anderson, who was 4th in 250MX points entering the day, looked to be on his way to a great race after nearly grabbing the holeshot in Moto 1. The Rockstar Energy Husqvarna rider settled into second place and was locked in a battle with Dungey. But Anderson soon began to fade, slowing down and losing a lot of positions in the process. He ultimately pulled off the track altogether.
Video from his battle with Dungey is below.