How high can flies fly?

Question

How high can flies fly?

Answer 1

Insects cannot fly much altitudes,

In fact, insects will seek out their ideal temperature for flying. If they reach a      height where it's too cold for them to fly, they simply fold their wings in and drop until      they reach a more comfortable cruising altitude.

Answer 2

good question..im not sure

Answer 3

As high as they want.