I was driving threw a canyon with a curving road. i first noticed it slightly forward to the left. the size and orientation stuck out in my mind. first it was shaped like a large triangle. not flat but very thick i would guess it was about 1/4 thick of one side of length. it was not flying level but was orientated with one tip straight down one tip up with the back side toward me. my first thought was it was a large aircraft banking in a turn, but i immediately noticed it was flying in a straight line. i recall noticing that it was not being carried by any helicopters and was not a balloon. it was moving at a high rate of speed like a fast moving aircraft. i had to make a couple turns on the highway and figured that i would get another look at the aircraft. but it was gone quickly and in the time frame that passed from my initial observation to when i should have got another look at it, it was gone i knew it was moving way too fast to for it to be towed, carried or floating in a wind current.