The DeLorean flies to the top story of Biff's Casino and Hotel
A hover conversion was an application to a ground vehicle to make it fly. The tires would be reworked to turn down for thrust, which came down through them. For the DeLorean time machine, lights were also placed in the tires and the rear louvers. Flying circuits were inserted into the vehicle. It is unknown if there was another source of lift other than thrust, such as anti-gravity or magnetism. Considering the loads that some vehicles produced, it is feasible that these could have been used.
Hoverboards were a legitimate use of this.
The technology was developed between 1985 and 2015.
In Hill Valley in 2015, a basic hover conversion cost around $40,000. Goldie Wilson III was a car salesman that turned ground vehicles into "skyway flyers".
The DeLorean hovers in 1985.
Doc converted his DeLorean sometime after traveling to 2015, but it is unknown if this was before or after he discovered Martin McFly Jr. and Marline McFly were sent to jail for being involved in a robbery plot. Doc also hover-converted the Jules Verne Train he built after becoming stuck in 1885, then going to 2015 to fit it.
Goldie Wilson's hover conversion commercial.
Behind the scenes
The $39,999.95 cost of a hover conversion is most likely a reference to Earl Scheib's television commercials in the 1980s. As the owner of the largest chain of low-cost auto body repair shops in the U.S., his well-known tagline in the 1950s originally stated, "I'll paint any car any color for only $29.99", but by the 1980s his price had increased to $39.99. The extra nines in the price of a hover conversion are a comment on the inflated prices expected in the future, and the marketing tactic of quoting prices just five cents less than a round number.
Appearances
The Jules Verne Train lifts up