No, Helicopters cannot fly in Stratosphere. It is too high for them. They do not produce that much lift. But they can fly in the Troposphere.
Yes, helicopters fly high when on long journeys.
They fly helicopters.
Because the air gets too thin.
usually helicopters that are operational at high altitudes, that are reliable, and that are cheap (small).
They fly in California.
You can fly helicopters.
There are many different helicopters. Most small civilian helicopters may fly for about an hour, but large passenger or military helicopters can fly for 6 hours or more.
so we can fly
No
Helicopters can fly directly up or down.
Yes, there are helicopters available.