Mumbai-Bound Ethiopian Aircraft Makes Emergency Landing Due To Cabin Depressurisation; Here's Why It's Alarming

In a mid-air scare, an Ethiopian Airlines flight ET640, en route from Addis Ababa to Mumbai, was forced to make an emergency landing recently after a cabin depressurisation incident. The Boeing 787 Dreamliner, cruising 33,000 ft over the Arabian Sea, experienced a sudden loss of cabin pressure, prompting pilots to descend rapidly. Upon landing, seven passengers were treated for decompression-related symptoms by the airport medical team.

In another incident, a Japan Airlines Boeing 737-800 operating flight JL8696 from Shanghai to Tokyo made an emergency descent from 36,000 ft to about 10,500 ft in under 10 minutes due to a cabin pressure alert. Oxygen masks were deployed, and panic ensued, with some passengers reportedly writing farewell messages amid fears of a crash. The plane safely diverted to Kansai International Airport in Osaka, landing at 8:50 p.m. All 191 passengers and crew were unharmed.

Before we delve into the concept, we must know that airplanes are pressurised to simulate a lower altitude, typically around 6,000 to 8,000 ft, even when the plane is flying much higher. This pressurisation is crucial for passenger safety, as it helps to prevent oxygen deficiency. This process is called cabin pressurisation, in which air is pumped into an aircraft or spacecraft to create a safe breathing environment for humans flying at high altitudes.

An aircraft cabin is the space where passengers and crew are accommodated. When cabin pressure fluctuates, it causes depressurisation, as was the case with the Mumbai-bound Ethiopian airline, which had to make an emergency descent.

Outlook Traveller reached out to aviation experts to understand why cabin depressurisation is alarming.

What Is Cabin Depressurisation?

Cabin depressurisation refers to a loss of air pressure inside the aircraft cabin, which is generally maintained at a level equivalent to 7,000–8,000 ft above sea level even when the plane is cruising at higher altitudes. This controlled pressure ensures that passengers and crew receive sufficient oxygen.

So when cabin depressurisation happens due to multiple reasons including air pressure leaking out of the cabin, an emergency descent at an altitude up to 10,000 ft (ideal for a human body to breathe) is the ultimate resort, shared Captain Shakti Lumba, former Executive Director of Alliance Air and Vice President of Operations at IndiGo.

"One must understand that cabin altitude and aircraft altitude are never same. An aeroplane flies at 30,000+ ft altitude, which is not an ideal state for human beings to breathe. That's why a cabin altitude is always maintained between 7,000-8,000 ft for a smooth oxygen flow for people on board," added Lumba.

What Happens During Depressurisation?

The air is too thin at high altitudes for humans to breathe normally. When depressurisation occurs, oxygen levels drop sharply. Passengers may experience hypoxia (oxygen deprivation) or breathlessness.

Elaborating further, Lumba explained that cabin pressure in aircraft is maintained at a lower altitude, equivalent to ensuring passengers and crew can breathe normally at high altitudes. While the aircraft may be at 30,000-40,000 ft, the cabin pressure is regulated to a level similar to that experienced up to 8,000 ft. This allows for sufficient oxygen levels and prevents hypoxia, a condition which can lead to dizziness, headache, unconsciousness and eventually death.

What Causes Depressurisation?

There are two types of depressurisation:

Slow/Gradual Depressurisation

It is often caused by a malfunctioning pressurisation system, which may not be immediately noticeable.

Rapid Depressurisation (as in the case of the Ethiopian airline)

It usually results from a structural failure, such as a ruptured window or a failed door seal, leading to a sudden drop in cabin pressure. Other causes may include a leak, system failure, engine bleed and rapid decompression in an aircraft, said aviation expert Captain Mohan Ranangananthan, a former airline instructor pilot.

"If there is any leak in the cabin pressure seal, the cabin altitude will go up beyond 14,000 ft (the maximum altitude at which a human body can breathe normally.) This means that the oxygen masks will automatically drop down. This is why we have oxygen masks for crew and passengers aboard," added Ranangananthan.

How Do Pilots Respond?

Ranangananthan explained, "When an aircraft's pressure fails, the pilot has to descend rapidly to bring the plane down to 10,000 ft and a naturally breathable atmosphere. It means that as soon as you descend to the required altitude level, you can easily breathe, even without the oxygen masks."

For the unversed, each row in an aeroplane has separate oxygen generators that last 12 minutes. That's why bringing the plane down as fast as possible during cabin depressurisation is critical to avoid a mishap. Lack of oxygen concentration in air can cause death in an instant, with brain death in the initial 15 seconds as soon as you run out of oxygen, added the aviation expert.

What Should You Do As A Passenger?

Commercial aircraft are equipped with automatic oxygen masks that deploy when cabin pressure drops. Pilots are trained to:

• Put on their oxygen masks IMMEDIATELY. This is a must.

• On the other hand, pilots must initiate an emergency descent and stabilise the aircraft at a safer altitude.

"For passengers with children, they must wear their masks first and then help their kids to avoid any adversity," said Ranangananthan. Most importantly, passengers must stay composed and follow crew instructions, ensuring their seat belts are fastened, especially when the plane is descending.