Leighton Orr graduated from the University of Pittsburgh with a bachelor's degree in mechanical engineering in 1928. Following graduation, he experimented with heat loss through glass block walls and double glazed windows. After working for six years at the Pittsburgh Testing Laboratory, he went to the Pittsburgh Plate Glass Company Research Laboratory in Pittsburgh, where he managed the physical testing department. Pittsburgh Plate Glass Company would change its name to PPG Industries, Inc., in 1968. Here he experimented with optics, heat flow, strength, safety, impact performance, and rating degree of anneal and temper in glass products; in addition he researched glass quality, types of defects, fracture analysis, selection of glass sizes, and thicknesses for wind loads on monolithic and insulating glass products; also receiving attention were issues of water loads on multiple laminated windows aquaria. Orr provided guidance to government agencies on the development of glass testing standards and fracture analysis of glass.
He retired from PPG Industries in 1972, but had a prolific career as a technical glass and ceramics consultant, in which he completed approximately 950 reports for clients as varied as architects, insurance companies, building owners, glass companies, developers and lawyers. Orr was sought out for his expertise in fracture analysis and breakage by high profile clients such as I. M. Pei and Partners, contributing work to Boston's John Hancock Center.
Orr was a member of the American Society of Mechanical Engineers (ASME) for over 60 years, where he received the distinction of being a Life Fellow. The University of Pittsburgh, School of Engineering made him a Distinguished Alumni in 1997, and placed him in the School of Engineering Hall of Fame.
Orr was 97 years old when he passed away on April 21, 2004 at the Concordia Retirement Home in Cabot, Pa. He had been busy doing consulting work until February, 2004. ASME established the Leighton E. and Margaret W. Orr Award for contributions to the literature on fractures and failure investigations as part of the considerable endowment Orr left them.