I got three days -- 300 dollars the first day and then 4000 the second. You need full radar and fuel suck. Rocket fuel & power and band strength are also very helpful.
I think the secret is to buy multiple upgrades at once -- if you don't have any acceleration and you buy the second one, all you pay for is the second (not first AND second) but you get both
Ah! I did it in 20 days... Try just going straight up and then down -- the up will get you the money for height and the down with increase your speed, getting you the speed achievement
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