Formed in 1958, Aeronautical Engineers Inc. (AEI) is the oldest conversion company in existence today. For more than 55 years AEI has provided advanced engineering solutions to aircraft owners and operators. As a global leader in passenger to freighter conversions for a wide array of aircraft, AEI has developed over 120 Supplemental Type Certificates (STCs), 385+ aircraft have been modified with AEI STCs – more than any other conversion provider.