This was done in Jersey about 15 years ago, except it wasn't call "crowd funding". A single half-page ad in the local paper invited people to call for a Prospectus, which had been approved by the financial authorities, and to buy as many £500 interest-bearing debentures as they wished in the new airline, called Islandair Jersey. Other perks were also offered, notably 2 free return seats a year to LGW.
About 350 residents did just that, investing a total of £285,000 within 2-3 weeks. They included most of the great and good, particularly financial movers and shakers. They probably accounted for 75% of the travel purchase decisions in Jersey.
The proposal was to recreate Jersey Airways with t/prop equipment, and take on Flybe, Aurigny and the embryo Blue Island head to head. It needed £2m working capital, at least, to get its AOC. Possibly nearer £5m, even then.
After failing to persuade the VCs and other lenders that few airline start-ups had such good backing and a ready market, the promoters returned the investments and killed the project.
Arguably, they failed due to lack of knowledge or experience of the finance industry, and should, of course, have drawn on the knowledge and expertise of their investors.
But it was a bold attempt.