TIP: If you want advance the fastest when you aren't playing be sure to give Ping its own window. Opening another tab in the same window can cause it to slow down or stop.
for those who cant beat it: after fully upgrading tilt your wing down until the wind resistance is 3% and use rockets until 200 mph. when your speed drops down to 175 use your rockets back to 200 mph and repeat until out of fuel. dont adjust tilt when out of fuel and you should reach 6000 easily