We were traveling north on US285 about 35 miles north of Roswell NM. A large triangular shaped craft appeared seemingly from nowhere and crossed in front of us very slowly from east to west. We didn't notice any lights or sound. It was flying very low to the ground and passed directly over our path. My husband is an electrical engineer who grew up in the air force the son of a USAF pilot and had served 11 years himself before getting out and going to work for defense contractors and performing EMP/EMI/EMC testing on military aircraft. He knew this was not a stealth or any other known military aircraft. My brother in law who was traveling with us served in the Air National Guard and had photographed dozens of military aircraft as a professional photographer, he did not recognize this craft either. After crossing over us the craft suddenly accelerated and was gone.