I did it in 15 days.
Here is my best beginning.
Acronyms:
For Shopping:
G - Glider,
R - Rocket,
RH - Ramp Height,
A - Acceleration,
AR - Air Resistance,
F - Rocket Fuel;
E.g. "Buy G3" = "Buy Glider level 3".
For Achievements:
D - Distance,
H - Height,
S - Speed,
T - Time.
St - Stage
Day 1. Buy nothing, Stage 5, Aim: earn $17.
2. Buy A1, St 5, Aim: Achieve D, $25.
3. Buy G1, St 5, Aim: H,T, $47. Hard day. You should fly up to maximum height but not slow down very much. You should catch the moment when to stop to ascend.
4. Buy A3, RH1, AR1, St 10, Aim: H,T, $120. The same as day3.
5. Buy R1, AR3, St 5, Aim: S, $180.
6. Buy F3, St 20, Aim: H,T, $310. See day3.
7. Buy G2, A2, AR5, St 10, Aim: D,S, $520. Easy.
8. Buy F5, RH4, St 35, Aim: H,T, $1030. See day3. It's important to earn $1000 to buy new glider.
9. Buy G3, St 20, Aim: D,S, $1000.
10. Buy R2, St 35, Aim: D,S, $1730.
11. Buy F8, A7, AR6, RH6, St 50, Aim: H,T, $3700
(Sorry, limit of 1000 chars)