At approximately 1500 Mountain time, the two aircraft collided during landing attempts to Runway 27 at the Los Alamos County Airport (KLAM). There were no injuries among the solo Commercial pilot of one airplane or the Airline Transport pilot and passenger of the other. Visual conditions prevailed. According to the solo pilot, he approached KLAM from the north, reporting his position on the CTAF. He did not receive any transmissions from other aircraft in the area. Approximately 10 feet above the runway, the pilot began to initiate his landing flare when he heard a “clunk” sound. The airplane began what the pilot thought was a landing roll; however, his airplane was still six to seven feet above the runway. Subsequently, the pilot observed another airplane underneath his. Both airplanes turned to the right and came to rest on the runway. The other pilot, also approaching KLAM from the north, reported his position, altitude and intentions on a different frequency.