Here is a non-exhaustive list of changes:
1) Improved aircraft handling, especially at low speeds.
2) Three new aircraft compared to the previous demo.
3) Three overhauled levels, two with extreme changes (Graphics Card and CPU).
4) Improved wind effects.
5) Simulation vizualization.
6) Flyby Camera
7) Reworked UX
8) Intro video explaining the story
9) Improved score vizualization
10) Improved unlocking system
...and lots, lots more!