Reality Change; A radical breakthrough was developed in gravitational understanding and technology.
Thus, engineers are able to create engines running off of gravity. As well as engines that create gravitational thrust.
The discovery and existence of this seemingly cleaner energy source begins to more or less dismantle the everyday fossil fuel economy as we know it.
What is a promising glimpse into a new era of technology is almost destroyed because of the long growing civil unrest erupting into a full flown conflict at the level of a 3rd World War.
A new technology race begins over which nation can first build the fastest, most destructive, and undetectable new weapon with gravitational technology.
With many sacrifices made, and martyrs memorialized, some scientists manage to get on track with putting this new technology towards everyday travel and space exploration.
Hover vehicles dreamed of in science fiction are finally invented, including bikes, boards, and cars.
Laws are then invented to try and gain control over the free use of such technology. Fly zones are established and new licensing programs put in place for gravitational hover vehicles.
Space ships are eventually made with gravity thrust engines, capable of faster and more maneuverable flight.