I was an airline pilot for 11 years. The Singapore Airlines incident shows why you should always wear your seatbelt.

• Captain Emma Henderson MBE was a pilot for Easyjet for over a decade. 
• She told Business Insider passengers should keep their seatbelts on at all times to avoid injury.
• It comes after a Singapore Airlines flight was hit by extreme turbulence, and one passenger died.

This as-told-to essay is based on a conversation with Emma Henderson MBE, a former EasyJet pilot. It has been edited for length and clarity.

I'm a former airline captain. I started flying 30 years ago when I was at University.

I became a first officer at EasyJet in 2009, and worked there for 11 years until I took voluntary redundancy in 2020.

The Singapore Airlines incident this week is a reminder that passengers should always wear a seatbelt when flying, even if the seatbelt sign is off.

This is for people's safety. The basic truth is that an aircraft is a hard surface, and people are soft.

Turbulence does happen, and when the aircraft moves around, if you are not strapped into your seat, you can move out of it.

A sudden movement of the aircraft down will result in you staying where you are in that space until you catch up with the aircraft. And it means you risk injuring yourself if you are not strapped in.

Turbulence can be unexpected

Aircraft are equipped with weather radar, which shows what's ahead of you. If there's water ahead, it paints it as a certain color on a screen; if there are hailstones ahead, it paints it as a different color.

Some of the weather radar systems on the newer aircraft that I operated can also show thunderstorms and turbulence.

However, it's not possible to see everything all of the time.

The reason it's recommended that seatbelts are fastened during the flight, even when the seatbelt signs are switched off, is because anything can happen at any time.

Even if you're flying in very clear air with good visibility all around you, an aircraft might have crossed your path a couple of miles ago, and you could fly through their wake, and you'll get a slight jolt.

Putting on a seatbelt just means you know that if anything should happen, you are much less likely to become injured.

Singapore Airlines incident

What happened with the Singapore Airlines flight was an extreme case. It's very unusual for something like this to happen in such a way.

When flying in an area like that, you're flying through areas with a lot of high-energy air movement and thunderstorm activity. And at this time of year there's a lot of heat in the atmosphere and a lot of moisture in the atmosphere.

So it sometimes is the case that you might be flying through weather and be aware that there is a risk, but there's not any immediate risk visible.

You can't climb above the clouds in that situation, and sometimes you just have to punch through them. You avoid the worst areas, but you can't see everything.

If you're flying in an area where there are very few other flights around, there's less information available. So it's unsurprising that something like this could happen and take people unawares.

Pilots are trained to deal with situations like this, and it's a testament to the high caliber of training of the Singapore Airlines pilots that even though they knew there were injured people aboard and one fatality on board, they were able to land safely in Bangkok.

They still brought that aircraft to a safe landing. Their training kicked in, and that's what you have to do.

My own experiences with turbulence

I've never encountered anything like what happened yesterday because it is so rare.

There are three different types of turbulence: light, moderate, and severe.

I have experienced moderate turbulence while descending through bad weather into Geneva, for example.

If you have to land somewhere, you don't have much choice. You will divert around as much of it as you can, but at some point, you may have to fly through quite bumpy weather.

When you're in the flight deck, and that's happening, you have complete confidence in your aircraft because you know it can withstand the extreme forces that it can be subjected to.

You trust your instruments, your aircraft, your instinct, and your skill.

I don't ever worry about flying, and even after the Singapore Airlines incident, I wouldn't worry about flying because I know it's so unusual.

I know the aircraft can withstand those forces and because I know everything about what happens on a flight, I don't worry about it.