List of Upgrades on Flight
Description: Improves the plane in general, and give you additional fuel.
Cost: $ 260 / 820 / 1900 / 2830
Description: Your plane becomes lighter, and falls slower.
Cost: $ 30 / 120 / 360 / 950 / 2140
Description: Your plane retains its velocity for longer
Cost: $ 40 / 170 / 480 / 1260 / 2750
Description: You can control your plane at the cost of fuel higher levels give you better control.
Cost: $ 80 / 290 / 650
Description: The initial power of throwing the plane is increased by 10 / 20 / 30 / 40 / 50 percent.
Cost: $ 90 / 180 / 430 / 900 / 1200
Description: Hold spacebar to activate your engine.
Cost: $ 130 / 480 / 1490
Description: Cranes now also give a boost.
Cost: $ 485
Description: Normal stars have an additional 2 / 4 / 6 percent chance to spawn as a gold star.
Cost: $ 150 / 375 / 1450
Description: Reduces fuel consumption by 10 / 20 / 30 percent.
Cost: $ 180 / 590 / 1350
Description: Your plane resists negative effects and gains boost from windmills.
Cost: $ 160 / 310 / 890
Description: Whenever you stall, you are given a chance to restart your engines.
Cost: $ 400
Description: Once per flight, you can turn all stars into rainbow stars for 10 seconds.
Cost: $ 1750
Description: Increases the duration of the crane bonus by 1 / 2 seconds.
Cost: $ 325 / 1250
Description: Jetstream warnings last 1-second longer.
Cost: $ 500
Description: A mysterious and impractical upgrade that is probably not worth the cost.
Cost: $ 3000
Recommended Build on Flight
2. Rudder Control
4. Throwing Power
5. Green Fuel
7. Better Model
8. Lucky Star
9. Crane Duration
10. Crane Booster
11. Fire Engine
12. Wind Detector
13. Emergency Booster
14. Rainbow Stars
15. Mystery Upgrade
Walkthrough Guide on Flight
My fastest record is 15 days for this game, Flight. My strategy is basically to fly at low altitude, then pick up speed by gliding through a windmill or take cranes repeatedly. This cycle can keep on going and last for insanely long, as long you got fuel to control your paper plane. Every bar of fuel can give you about 1000 meters, just imagine if the game implements fuel pickups. The game is self-sustainable! The "Mystery" Upgrade is not that bad. What it does is it makes your plane turn into some origami animal (I've seen the Learn to Fly's Penguin and Toss the Turtle's Turtle), which makes you bounce forward some more, hitting cranes, stars, and those propeller things.
Lastly, to grab lots of space stars. Try to max out all your upgrades first. Pick up your plane, go to the bottom left the corner, then throw quickly towards the top. Immediately hold left and space, so you should fly close to straight up. When you have about 1 bar of fuel left, stop using the engine. You should stall. Use emergency stall; now you're flying horizontally at some crazy high altitude, and you can use the rest of your fuel to aim for space stars. By the way, do not ever throw backwards.