I once saw a bright airborne light appear over the Mojave desert late one summer night. I was on FF with LA Center. They saw nothing on radar.
My pilot/passenger also saw it. Looked like very bright landing light pointed at us a few miles off. We flew about 290 minutes and it’s appearance remained equidistant. LA monitored and never saw it on radar.
After about 20 minutes it ‘shot up’ what appeared to be straight up and vanished in moments.