Because the air gets too thin.
Helicopters can fly directly up or down.
Yes, helicopters fly high when on long journeys.
Helicopters are typically designed to fly in the troposphere, which is closer to the Earth's surface. The stratosphere begins at around 10 kilometers above sea level, and helicopters lack the necessary design and power to operate efficiently at that altitude.
Because rotors are noisy and helicopters isually fly close to ground
They fly helicopters.
Most helicopters fly with only one rotor. If you mean one blade, that is because it would be unbalanced.
You can fly helicopters.
They fly in California.
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.
No
so we can fly
Yes, there are helicopters available.