The only way flying cars will EVER be viable is three techs will be needed.
1. Compact Portable and SAFE Electrical power source, ie, portable fusion, or ZPE of whatever.
2. Anti-Gravity type propulsion that is cheap and compact.
3. Automated Computer with guidance and collision control software that is very tested.
We only have ONE of those....so as far as we KNOW....
With #2 all else is unnecessary................