why don't planes fly at lower altitudes which has breathable air outside in case of any emergency?

Question

If you are flying at lower altitudes which has air outside which humans can breath why dont planes fly at that altitude in case of any ermergency eg. a broken window or something.

Answer 1

The above answers about the fuel consumption are correct.
However the main reason aircraft started flying high was so they could be above the weather.
Most of the atmosphere's weather is 18,000 ft and below.
Flying above it increased passenger comfort enormously.
I believe the first person to actually have the idea was Howard Hughes.
Once they were able to get airliners that high the fuel savings and extra speed kind of fell in line.
So yes it does save fuel but the original idea was passenger comfort.
By the way an airliner has to be able to get down from altitude within a specific period of time if there was a cabin decompression. The new airliners that are flying up to 50,000 ft are in a whole new category. I am not positive, someone may correct me, but I think the standard is 10 minutes to get to 12,000 ft asl from cruising altitude.

Answer 2

The increase in the Earth's circumference at 36,000 feet above sea level is only about 0.08%, so it is not significant for air travel. There are two main reasons for flying at high altitude. The first reason is that it's cheaper. The higher you fly, the thinner the air becomes, and so the less air resistance that you have to overcome to fly. This in turn means less thrust required, and thus less fuel burned. The extreme is when you leave the atmosphere entirely, at which point there is no air resistance and you don't need any thrust to continue moving. At high altitudes, you can fly faster while burning less fuel than at low altitudes. The second key reason is that flying high keeps you above most of the weather, which reduces turbulence and diminishes the likelihood that you'll have to detour or delay a flight. There are some other minor reasons. One other advantage to flying high, for example, is that there's nothing on the ground you can hit. At 36,000 feet, you're above everything, even Mount Everest. This means you can plan and fly routes without worrying about terrain.

Answer 3

THEY DO.

In the event of loss of air pressure in the cabin (due to a broken window for example), the pilot in command will initiate an emergency descent to 14000ft where the air outside is breathable. However if the plane is at crusing altitude it can take 6 or 7 minutes to descend to this altitude so this is what the drop down oxygen masks are for.

Answer 4

In lower altitude drag force is great so the consumption of fuel very worst because the air pressure to high in lower altitude

Answer 5

Because of many reasons. Each plane is designed to fly at different altitudes, like a large Boeing 777 cant not fly at lower altitudes, or it will lost control and crash. The aircraft's altitude affects where there is aircraft radio frequency. The aircraft uses less fuel when flown up high around 20,000 - 50,000 ft. Also the plane cannot fly fast enough to continue in low altitudes. Higher altitudes result in less aircraft noise pollution, and crashing into tall buildings. Some planes' Auto-Pilot system cannot maintain control of the aircraft at the height below 17,000 ft. There are also many more technical, scientific explanations why. If planes could fly lower, aircraft technicians and designers would have noticed.

Answer 6

Speed and efficiency, as others have said.

Up to the low 30 thousands the aircraft speed is limited by indicated air speed, above that it is limited by mach number (a huge over simplification). The IAS is way below the true air speed, so at 30,000 feet you might see 300KIAS but a 450TAS, so you are covering way more ground. The engines also burn less fuel at altitude, so an engine that burns 40,000 pounds per hour at sea level may burn under 20,000 at cruising altitude.

This has a huge impact on range, a 777 taking off from SFO to fly to LHR wouldn't make it at 20,000 feet.

Answer 7

Thinner air at higher altitude, which means more efficient for the engines, and cooler temps, also the air is smoother.

Answer 8

The air is much thicker than higer up which costs more in fuel consumption and range add to that the simple fact that they wont be able to go as fast due to same reason.

Answer 9

For a number of reasons. The main ones being speed, fuel efficiency, and to get around (above) weather.

Answer 10

They get better fuel efficiency do to the thinner air plus greater speed for the same reason.