correct me if I am wrong
you did three years already and want to do another 3 (total 6) in uni
no wonder your parents want you out of their wallet
as an employer I would wonder about a student spending six years in uni (unless its germany where they don't seem to graduate until 30)
if you want to do aviation, keep the manufacturing degree (good to have, as it is broad and aviation industry is cyclical) and use the 3 years you have assigned to get your engineers licence, you will be much more employable than a person with two degrees (and also you'll earn some money while being an appi, ah the memories of cleaning A300 toilets and other fun appi jobs )
Degrees only get your foot in the door, hard work and practical experience (that includes being an appi) get you the money and more respect