Question

Why passengers planes fyl at low altitudes?

Answer 1

Planes equipped with jet engines fly at greateraltitudes than propeller-driven aircraft. These include commercial flights,
cargo jets and even private passenger jets. The air traffic control tower
usually assigns a cruising altitude of up to 39,000 feet, but long flights are
typically assigned higher altitudes. By keeping these planes at assigned
altitudes, air traffic control creates invisible stacked highways in the sky,
keeping enough air space between the flights. Air traffic control may change an
aircraft’s altitude assignment as needed.
Most general aviation planes use propellers and mustcruise at lower altitudes. For example, a Cessna Skyhawk has a maximum
operating altitude of 13,500 feet. Planes that fly at higher altitudes must
have pressurized cabins to keep the pilots and passengers safe and comfortable.
The pressure and oxygen levels inside the cabin are set to correspond with
those experienced at up to 7,000 feet.
Also for most commercial passenger aircraft, the cruisephase of flight consumes the majority of fuel. As this lightens the aircraft
considerably, higher altitudes are more efficient for additional fuel economy.
However, for operational and air traffic control reasons it is necessary to
stay at the cleared flight level. On long haul flights, the pilot may climb
from one flight level to a higher one as clearance is requested and given from
air traffic control. This maneuver is called a step climb.