Why do aircraft typically cruise at 35,000 feet? Why this height and who decided?

Answer 1

There are a number of reasons for this. First off, it's typically commercial airliners flying at or near this alititude. One reason is because the air is thinner, less fuel would be consumed, less air traffic (no smaller aircraft), and often times the ride is more smooth! The altitude an airliner flies at often times decided by the air traffic controllers, though the pilots do report on the turbulence. If the air traffic controller specifies 32000 feet, and the pilot reports turbulence, the pilot can request for a higher altitude, but ultimately, the air traffic controller decides whether or not to approve that request, and takes into account other reports of turbulence at that same altitude, and uses this when considering wheat altitude to request other pilots to fly at as well.

One more thing to note - When traveling east, the altitude will be an odd numbered thousand (33,000 feet, 35,000 feet, 37,000 feet) When traveling west, the altitude will be an even numbered thousand (32,000 feet, 34,000 feet, 36,000 feet) this is to maintain vertical separation.

You might only typically cruise at 35,000 feet if you typically fly east. :)

Answer 2

Lots of reasons really but they do not all fly at 35,000 feet. It would get real crowded up there if they did. The higher altitude is for prevailing wind currents better fuel burn and so if a catastrophic failure happens they have time to establish best glide to an airport or attempt a restart. At a low altitude you have no or very little glide time so if you lose your engines you go down and I mean fast. Aircraft fly at different altitudes depending on direction of travel. North South would be an even number plus 500 feet and East West might be an odd number plus 500 feet to assure aircraft separation. Air traffic control assigns altitudes in controlled airspace. A Pilot may however deviate from that altitude for the safety of the Aircraft and passengers.

Answer 3

The colder the air temperature, the more efficiently turbojet engines can operate. The coldest air is found at the atmospheric level of the tropopause. Here, the ambient air temperature decreases by about three degrees every 1,000 feet and stops dropping at around 70 degrees below zero. The altitude of the tropopause varies with the latitude and the season. At the North and South Poles, the tropopause is as low as 30,000 feet. It slopes upward to 60,000 feet at the equator. Due to the low atmospheric pressure at this altitude, the air density is less than one-third of that at sea level. This reduced density allows the aircraft to fly much faster than it could if the air was as thick as it is at sea level. Because the air at cruise altitude is so cold and dry, the water in the jet exhaust creates ice crystals, which leave behind the familiar streaks in the sky called condensation trails or contrails.

The direction of the flight will also be a consideration in the cruising altitude. Eastbound aircraft fly at odd thousands, such as 33,000 and 35,000 feet. Westbound aircraft fly at even thousands, such as 34,000 and 36,000 feet. This staggering of altitudes provides at least 1,000 feet of vertical separation between two converging aircraft.

Answer 4

Different Aircraft fly at different altitudes. The higher you go there is less air for the plane to get get lift. It all depends on the type of aircraft. 35,000 feet is typical for most jet, but smaller non-jet planes can't go near that altitude. Its all about balancing act between drag, lift, and fuel efficiency.

Answer 5

Engine operating efficiency and fuel efficiency are optimized at these altitudes. The air is thinner so there is less drag. The actual altitude is determined by the ATCs (Air Traffic Control Centre).
Safety. If there is engine failure at high altitude, there is more time to recover or restart. The cruising range is greatly increased at higher altitudes.
Winds are typically less severe. There are optimum altitudes to minimize head winds which slow you down and burn more fuel. There is typically less turbulence at higher altitudes but there is a phenomenom known as clear air turbulence, rare.

Answer 6

Its a trade of between air resistance and lift.

Flying high reduces fuel usage, flying too high reduces air lift and requires higher angle of attack - reducing speed.

35,000 is a generic term, there is a whole band of heights used centred around this figure.

Answer 7

The reason they cruise here is because the air is thin, meaning less drag so lower fuel consumption, but the air is thick enough to keep the plane up.

Answer 8

Aircraft cruise at that altitude, because the air is thinner and they use less fuel!

Answer 9

Because that's the jet stream: really high, strong winds. The the air is a lot thinner, so you can go faster. If the plane flew at say, 10,000ft it would take nearly 3 times as long to get there.

Answer 10

LOVING FATHER left a great answer! Thanks so much for the info! Im really surprised as to how many people knew the answer to this question! Thanks to the person that asked it too! Ive always wondered the same thing! Someone who has a high rating....mark loving father as the BEST answer!