Riddle Airlines DC-4. Riddle Airlines began operations in 1945 as a non scheduled carrier. Later as a mostly all cargo airline it began scheduled operations and flew passenger/cargo flights for the US military. Riddle flew C46s, DC-4s, DC-6s, DC-7s, DC-8s and Armstrong Whitworth Argosy turboprops. The name changed to Airlift International in 1963. Airlift acquired Slick Airways in 1966 and managed to survive several bankruptcies only to go under for good in 1991. Riddle was founded by John Paul Riddle, also a founder of Embry-Riddle Aeronautical University of Prescott, Arizona and Daytona Beach, Florida.