Cabin pressure and ear pressure: what happens on a plane

The plane starts its descent, and suddenly one ear feels packed with cotton. For some people it stays a mild pressure, while others sit in their row with stabbing pain. Behind the phenomenon is cabin pressure – and a tiny channel in your head that does not always keep up with the pressure change. This article explains what cabin altitude is, how the pressurized cabin of an airliner works, why landing in particular is hard on your ears and what you can do about it.

Cabin pressure: the short answer

An airliner in cruise moves at altitudes where a person without help would lose consciousness after a short time. That is why the fuselage is pressurized – but not to sea-level pressure. The US certification rule for large transport aircraft (14 CFR § 25.841) requires the cabin to hold a cabin altitude of no more than 8,000 feet in normal operation, that is, about 2,440 meters. Why jets climb so high in the first place is explained in the article Why planes fly at around 10,000 meters. The European design rule for large aircraft is set up the same way on this point.

So in cruise, you are effectively sitting on a mountain. According to the standard atmosphere, air pressure is then around 750 hectopascals instead of about 1,013 at sea level. Healthy people notice little of this in everyday life. But your ears certainly notice that this pressure drops when climbing and rises again when descending.

What cabin altitude actually is

The term is often misleading. Cabin altitude (also called cabin pressure altitude) is not an altitude measured anywhere, but a converted pressure value: it indicates at which altitude in the International Standard Atmosphere the air pressure is the same as in the cabin right now.

An example: the jet flies at 38,000 feet. Outside, the air pressure is only about 200 hectopascals, roughly a fifth of the sea-level value. Inside, the pressurized cabin holds about 750 hectopascals. That corresponds to 8,000 feet – so the cabin altitude is 8,000 feet, while the aircraft is 30,000 feet higher up. The fuselage has to withstand the difference between inside and outside pressure on every single flight.

Altitude (standard atmosphere)	Altitude in meters	Approx. air pressure	Share of sea-level pressure
Sea level	0 m	1,013 hPa	100 %
6,000 ft	≈ 1,830 m	≈ 812 hPa	≈ 80 %
8,000 ft	≈ 2,440 m	≈ 753 hPa	≈ 74 %
10,000 ft	≈ 3,050 m	≈ 697 hPa	≈ 69 %
15,000 ft	≈ 4,570 m	≈ 572 hPa	≈ 56 %
38,000 ft (cruise)	≈ 11,580 m	≈ 206 hPa	≈ 20 %

The values are calculated with the standard atmosphere and rounded. Real weather shifts the outside pressure by a few hectopascals, which does not change the principle.

How the pressurized cabin works

The principle is simpler than you might think. The fuselage is a largely airtight pressure vessel, closed off at the front and rear by pressure bulkheads. Air is continuously pumped into this vessel. On most airliners, this is compressed air from the engines, which is cooled and conditioned before it is fed in. How this air is composed and filtered is described in the article Cabin air explained.

The pressure is regulated not through the supply but through the outflow. At least one outflow valve sits on the fuselage, and the cabin pressure controller opens it more or less. The wider it is open, the more air escapes and the more cabin pressure drops. When it closes, pressure rises. This way, the cabin altitude can be raised gently during the climb and lowered again during the descent, instead of jumping abruptly with the flight altitude.

Why not just sea level?

Because every pressure difference puts load on the fuselage. The higher the inside pressure in cruise, the greater the difference to the thin outside pressure and the sturdier – and heavier – the structure has to be built. Every flight is also a full load cycle: pump up, hold, release. How dangerous it can be to underestimate this was shown in the 1950s by the De Havilland Comet (type profile: DH.106 Comet), whose accidents were largely attributed to metal fatigue from repeated pressure cycles. The cabin altitude of up to 8,000 feet is a compromise between passenger comfort and structural weight.

Newer types show that this compromise can be shifted. For the Boeing 787-9 and its siblings, Boeing quotes a cabin altitude of about 6,000 feet – made possible, according to the manufacturer, by the fuselage made of carbon-fiber-reinforced plastic. For the Boeing 777-9, too, Boeing has carried over the lower cabin altitude – that is, the higher cabin pressure – from the Dreamliner program. In the business jet segment, cabin altitude is even openly advertised: Bombardier quotes 4,850 feet at a flight altitude of 41,000 feet for the Challenger 3500.

A bit of history

The idea is older than the jet. The first airliner with a pressurized cabin in scheduled service is considered to be the Boeing 307 Stratoliner, which made its first flight in late 1938 and entered service in 1940. It could fly above much of the weather, although its cabin altitude was still well above the values of today’s jets. Since then, the pressurized cabin has been standard on everything that regularly climbs to high altitudes.

The pressure profile during a flight

For your ears, the absolute cabin altitude is not what matters, but the change. A typical flight runs in four phases:

A nice proof of the physics behind this: a plastic bottle that you screw shut in cruise is crushed after landing. It has trapped the thinner cabin air, and the higher pressure on the ground squeezes it. With bags of chips, the opposite happens – sealed on the ground, puffed up in cruise.

Why your ears feel pressure

Between the eardrum and the inner ear lies the middle ear, a small, air-filled cavity. It is connected to the nasopharynx via the Eustachian tube. At rest, this channel is closed, and it opens briefly when you swallow or yawn. Only then can air flow in or out and adjust the pressure in the middle ear to the surroundings.

During the climb, cabin pressure drops. The air in the middle ear now has more pressure than its surroundings, expands and pushes the Eustachian tube open from the inside. Equalization usually happens by itself, often with a soft click.

During the descent, it is the other way around. Cabin pressure rises, and the lower pressure stays behind in the middle ear. The eardrum is pulled inward, and the Eustachian tube does not open passively – it has to be opened actively by swallowing or yawning. If that fails, you get a noticeable feeling of pressure, later pain. Medically, such pressure-related damage is called barotrauma of the ear.

According to the US health library MedlinePlus, typical symptoms are a feeling of fullness in the ear, pain, slightly muffled hearing and sometimes dizziness. In the vast majority of cases, the hearing loss is temporary and goes away by itself. The US health agency CDC lists a ruptured eardrum, persistent hearing loss or ringing in the ears as rare, more serious consequences.

Who is especially affected

Anything that makes the mucous membranes in the nasopharynx swell makes equalizing harder: a cold, sinusitis, hay fever. Children also have a harder time because their Eustachian tube is narrower and they cannot consciously control pressure equalization. And if you sleep deeply during the approach, you swallow less often – MedlinePlus therefore explicitly advises not sleeping during the descent.

What helps against ear pressure

The good news: for most people, simple remedies are enough. The most important trick is timing – start as soon as the aircraft begins its descent, not only when it already hurts. A common cue is the crew’s announcement that the approach is starting, or the engine noise becoming audibly quieter.

Many people know the active pressure equalization maneuver from diving. The important word is gently: the aim is to nudge the Eustachian tube open briefly, not to force air into the ear with maximum force. If it does not work, a combination often helps: swallow while holding your nose, then go back to breathing normally.

Flying with babies and kids

Infants cannot swallow on purpose to equalize pressure – but they do it while drinking. The CDC recommends letting babies nurse or drink from a bottle during the flight. This helps most during descent. Older children can chew gum or drink something. On medication, the CDC is clear: antihistamines and decongestants are not proven to be effective for children in this context, and US medical societies explicitly advise against them for young children. If you go on a spotting trip with kids, you will find more tips in the article Plane spotting with kids.

Cabin pressure and health: what else matters

For healthy travelers, the lower cabin pressure is usually not a problem. According to the CDC, it can aggravate symptoms in people with certain heart, lung or blood conditions because less oxygen reaches the blood. If you are affected, have your fitness to fly checked by a doctor before the trip. If someone needs supplemental oxygen on board, this generally has to be arranged with the airline in advance.

Then there is the dry cabin air, which the CDC puts at about 10 to 20 percent relative humidity. Dry mucous membranes do not make pressure equalization any easier either – drinking regularly helps twice. On long routes, time zone changes and sleep rhythm also play a part; tips are in the article Avoiding jet lag.

Diving and flying

If you dive on vacation, you have to take cabin pressure into account. The diving medicine organization Divers Alert Network (DAN) recommends a break of at least 12 hours before flying after a single no-decompression dive, and at least 18 hours after several dives in one day or on several consecutive days of diving. After decompression dives, a much longer break is advised. The background: the lower cabin pressure can make nitrogen dissolved in the body come out of solution.

When cabin pressure drops

A sudden loss of pressure is rare, but that is exactly what the yellow masks are for. The US certification rule requires the cockpit crew to be warned as soon as the cabin altitude exceeds 10,000 feet. On aircraft that are allowed to fly above 30,000 feet, the oxygen masks for passengers must drop automatically before a cabin altitude of 15,000 feet is reached. In such a case, the crew can also set an emergency code (more on that under Squawk codes 7500, 7600 and 7700) and starts a rapid descent to an altitude where people can breathe again without supplemental oxygen.

For you, the rule is: put your mask on immediately, and only then help others. There is a reason the safety briefing before every flight explains this in such detail – at high altitude, there is only little time in which you can act clearly. If thoughts like this make you nervous, the article Understanding and overcoming fear of flying offers helpful perspective. The question of why it sometimes gets bumpy is answered by an article of its own: Turbulence explained.

For spotters on the road

If you take spotting trips by plane, you sit in the approach more often than most passengers – and usually want to shoot out of the window rather than struggle with ear pain. A few habits help:

• Keep a drink within reach. A bottle of water in the seat pocket before the descent saves fumbling around when the camera is already in your hand.
• Chewing gum instead of a break. Chewing goes on in the background while you look through the viewfinder. You can find the right seat for approach shots in the guide Choosing the best window seat for photos, and technique tips are in Photographing from the airplane window.
• Got a cold? Check plan B. If the trip can be postponed, that is often the better idea with a stuffy nose – the same goes for the return trip.
• Book newer types on purpose. If you have the choice, you will definitely notice the difference between an older medium-haul jet and a Dreamliner or Airbus A350-900 on a long-haul flight – not only in your ears, but in how you feel overall after the flight.

You can find more on preparing longer tours under Planning a spotting trip.

Conclusion

The cabin of an airliner is a controlled compromise: enough pressure for you to breathe comfortably, but not so much that the fuselage would have to be needlessly heavy. A cabin altitude of up to 8,000 feet is permitted, and newer types stay below it. For your ears, the descent matters most, because the Eustachian tube then does not open by itself. If you swallow, yawn, chew or gently equalize in time and stay awake on the approach, you will in the vast majority of cases arrive on the ground without discomfort.