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We’re well into the swing of summer and, to reach those destinations that are more than a train or car ride away, flying is a popular travel option.

When you're up in the air, looking at the white fluffy clouds, you may wonder about the science of it all. But there are some other practical questions that often pop up when we're on a plane.

Commercial pilot Harkirit Singh Gill has answered five of these popular questions. So sit back, relax and enjoy being whisked away on a journey full of fun flying facts.

Why do our ears pop when taking off?

It's one of those moments that make most of us go 'oh!', but why do our ears tend to pop when we take off on a flight?

Harkirit explains: “It’s all to do with air pressure. The air that we are all used to on the ground is more dense than the air that is around us when we fly. As you go higher up into the atmosphere, the air pressure reduces.”

Think of air having lots of invisible particles that we can’t see; on the ground, there are more of these invisible particles because of the weight of the air above it pushing them down, which squeezes the particles into a smaller space, making the air very dense. As you go higher up in the sky, the weight pushing down on the air reduces, which means that these particles are more spread out and makes the air less dense.

So what does that have to do with our ears? Harkirit explains that behind your ear drum you have something called the Eustachian tube. This has air trapped inside it all the time. When you take off, the air that is inside your Eustachian tube, which is the dense, high pressure air from ground level, is trapped inside. But the air outside your ear drum is the less dense, low pressure air. Air likes to move from areas of high pressure to low pressure. This makes the air in your Eustachian tube push against your ear drum until suddenly the air is released, which makes that popping sound which none of us like.

Harkirit’s top tip to help you pop your ears yourself is to take small sips of water, have a hard-boiled sweet, or try yawning.

Where does toilet waste go when you flush on a plane?

If you've been to the toilet on an airplane, you may have noticed the powerful vacuum effect that can take you by surprise when you flush. That happens due to the difference in air pressure in the toilet compared to the plane.

Harkirit explains the loud noise is actually a really powerful vacuum which sucks away all of the waste inside the toilet bowl: "The toilet on an aeroplane doesn’t have water inside the bowl, like the toilet you have at home, because the suction of the vacuum is powerful enough in itself.

"Your toilet at home uses gravity to push the water through the pipes, but at high altitude, there is less gravity. This could mean that not all of the waste inside the toilet is flushed away properly, which could be quite smelly for the next person who uses it.” Harkirit also highlights how, if we did have water inside the toilet, things could get a bit messy when the aircraft experiences turbulence.

You may now be wondering what happens to what's flushed down the toilet. Some think it’s released into the air out of the aeroplane, but that's not the case - it's stored in a sewage tank at the back of the aeroplane. It can only be accessed on the ground, and the process of disposing toilet waste after a flight involves using a lavatory service cart, which drains the tank, ready for the next flight.

True or false: The pilot and co-pilot can’t eat the same meal

This one may seem rather bizarre; imagine the awkwardness if they both really want to eat the same thing. But it’s all for a good reason. Harkirit explains that, by making sure the pilots eat different meals, if one of them gets food poisoning, the other one is well and ready to take over and fly the plane.

Who knew choosing the roast chicken or the lasagna could have such an impact?!

True or false: Pilots don’t need to look out of the window when flying

Looking out of a window is crucial when driving a car, but it's not quite the same for planes once they're in the air. Harkirit explains that planes are flown through advanced technology which makes looking out of the window unnecessary. Flight instruments are displays which can tell the pilot different things, like airspeed, altitude, directional heading etc. These are all controlled by complex sensors which are extremely reliable. "Unlike driving a car, there are no road signs to tell you where you are in the sky," he says. "The way that pilots know that they are flying straight and level is all thanks to their instruments.

"The pilot would normally only need to look out of the window when coming in for a landing, although on some planes, technology has become so advanced that the plane is able to land itself! Your pilot would have gone through years of training, so just know that you are always in safe hands."

Why are plane seatbelts different to car seatbelts?

Even though you’re sitting in the same way that you would when in a car, plane seatbelts are quite different. This is because car seatbelts are designed to keep your body upright in the case of an accident, whereas plane seatbelts are designed to keep passengers secure when turbulence occurs. Harkirit explains that on a plane “the main movement experienced is an up or down motion. This means that there is no need for a shoulder harness, as a lap belt would be enough to stop you being lifted out of your seat”.