One advantage is that there is usually less turbulence at higher altitudes. I think because you are flying higher than those "pockets" of turbulence that you experience at lower altitudes.
This question does not provide enough information to be answered.
High altitude particulate pollution may be helping to reduce global warming.
A helicopter cannot reach a plane's altitude because it does not have much lift. No, the air is to thin high up for a helicopter to sustain flight.
Not sure but it might have been the SR-71 Blackbird.
During IFR flight, ATC will dictate cruising altitude.
it's altitude should be whatever is economical for that flight
It cruised about 60,000 feet, so that's about as high as it would go.
We will fly a VFR flight heading 245 - what is a legal cruising altitude?
1000 feet
That sort of depends on the design of the propeller in question, but in general, propellers excel at low speed flight and short field takeoffs. Limitations are in high speed performance (efficiency drops sharply near the speed of sound), and maximum altitude they can attain.
As the sky is always at the same altitude there are neither advantages or disadvantages.
You get a High-Altitude In-game Flight suit. You can watch comerrcials on T.V. too explaining it.