Dr. Chuck Cross, Chief of Turbine Engine Division, Aerospace Systems Directorate, Air Force Research Laboratory, presents a book to Mr. Ian Whittle containing an excerpt about his father, Sir Frank Whittle during a tour of AFRL at Wright Patterson Air Force Base, Ohio. Oct. 31, 2017. Whittle's father is credited for inventing the gas turbine engine effectively launching aircraft propulsion into the jet age. (U.S. Air Force photo / Lisa Donauer)