my husband and i were traveling south on i15 in nevada in our semi. when he noticed a blue contrail heading nw. he pointed it out to me and when i glanced in the direction i saw a blue light, from our distance it looked the size of a golf ball, it was going in a upward path then changed course within a split second, the contrail stopped then it took off again and then vanished. i am a photographer and have witnessed some odd stuff but i have never seen anything like it. meteor maybe, but i doubtful, as it flashed, pulsed and left a very wide blue contrail. once it vanished we noticed not one but five air craft within a mile from the sighting heading the direction we seen it.