Yes
The maximum height at which a passenger aircraft can fly is 40000 feet.
It is rare for airliners to fly that high, the general range is 35-40k feet. The reason they fly this high is because the air is less dense (pressure is lower) this allows the aircraft to travel faster and with less drag, thus increasing fuel efficiency.
No.
These days passenger jet aircraft are the norm
Concorde was a passenger aircraft. It was developed by five different countries. It is the only passenger plane to fly faster than the speed of sound.
Most commercial passenger airplanes typically cruise at altitudes between 30,000 and 40,000 feet. The maximum operating altitude for many large jets is around 45,000 feet, while some specialized aircraft can fly higher. Factors like air traffic control regulations, aircraft design, and passenger comfort limit cruising altitudes. Ultimately, the altitude is chosen to balance fuel efficiency, safety, and air traffic considerations.
Aircraft typically arrive at an altitude of around 30,000 to 40,000 feet to operate and fly.
Commercial, jet engined aircraft, such as the 747, fly at approximately 40 000 feet. Propeller aircraft fly at lower altitudes
Most aircraft do not travel in the stratosphere. Some military and passenger jets fly in the stratosphere, but most aircraft fly in the troposphere, below the stratosphere.
Passenger planes can't fly at 55,000 feet. Gulfstream business jets can fly 51,000 feet altitude, and airliners like to cruise at 35,000 feet. Some military planes, like the U-2, can fly at 55,000 feet or greater.
Because the pilots, staff and passengers would pass out from lack of oxygen at the altitudes that aircraft fly best. Aircraft cabins are usually pressurized to 8,000 feet altitude equivalent. This also reduces passenger inner-ear discomfort.
Most aircraft fly in the 'Troposphere' which exist up to approximately 55,000 feet. After that is the' stratosphere' which only a few military aircraft fly in.