On April 19, 2006, approximately 1000 mountain daylight time, a Cessna 310R, N954EA, sustained substantial damage when the right main landing gear collapsed during the landing roll on runway 28R at Billings Logan International Airport, Billings, Montana. The commercial pilot and the two passengers were not injured. The airplane was registered to and operated by Exec Air Montana Inc. of Helena, Montana. Visual meteorological conditions prevailed and a company visual flight rules flight plan was filed for the 14 CFR Part 135 flight. The flight originated from Helena, approximately 0900. According to the pilot, the approach to landing was normal, and she verified that all three landing gear were down and locked. Following a normal touch down, during the landing roll out, the right main gear collapsed. An FAA inspector examined the airplane and reported that the right aileron was damaged and required replacement. The reason for the collapse of the landing gear was not determined.