There's already an STC (Supplemental Type Certificate; permission from the authorities to modify or operate an aeroplane in a way that is different from when it

There's already an STC (Supplemental Type Certificate; permission from the authorities to modify or operate an aeroplane in a way that is different from when it was manufactured) which allows the use of regular gas (literally, from a gas station) in many different planes - https://www.autofuelstc.com/ https://www.autofuelstc.com/.