I just noticed that when planes takeoff after leaving the ground, the plane steeply climbs up altitudes, however, before it touches down, the plane this time smoothly descends to the ground. Why is that the case?
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When landing, the descent has to be a careful balance between losing speed and altitude, but doing so in such a way that the plane still has enough lift to remain in the air, but then contact the ground gently enough to not damage the aircraft or its passengers. It’s pretty complicated to take something that heavy and have it safely transition from a thing flying fast through the air, to a thing that is on the ground and not flying at all, without damaging anything.
When taking off, they want to reach cruising altitude and clear the airspace around the airport as quickly as possible. That’s where the traffic is, so it’s best to clear the area quickly. There is also better fuel efficiency once they’re at altitude and cruising speed.
Note: I’m not a pilot but have always been fascinated by aviation and feel I can answer this. Landing and take off are both dangerous periods of time for an aircraft. I head a saying once: “for a plane speed is life, and altitude is life insurance.” A plane maintains flight by moving forward through the air and creating lift, if it slows down too much it will start to fall. Let’s say a plane’s engines all fail. If it’s high up it can glide for a long way looking for a safe landing, constantly trading some of its altitude for speed to stay flying. But if the plane is low there’s not going to be much gliding before it meets the ground.
When planes are on a landing approaching they aren’t using much power and are kinda gliding in, again constantly trading altitude for speed. Keeping the final approach long and low allows them to touch down softly and keep their speed up should they need to abort the landing. Check out [this video](https://youtube.com/shorts/Y3rEIPC_HXA?feature=share) showing the difference between air force and navy pilots landing their jets. The navy pilot takes a steeper approach and really slams the plane onto the runway, while the air force pilot tries to let the wheels touch before weighting them. The reason for this is that navy pilots learn to land on aircraft carriers where they don’t have the liberty of a long runway.
In regard to climbing quickly on take-off, again think of what the plane needs. It’s been blasting down the runway on full throttle to build up enough speed to liftoff. Once it can fly it needs to maintain that speed, but quickly gaining altitude is building up that life insurance. Say you have an engine failure one minute after takeoff, gaining as much altitude as you can in that time means you’ve got more gliding to work with to get back to safety.
take off is a matter of performance. If you have the power to do so, you want to go up ASAP to reach those juicy altitudes that gives you low fuel consumption. Each plane type, company, and loadout has its way to do it.
Landing is a matter of safety: you commit to a runway using a “stabilized approach”. It means, you are aligned with the runway and you descend a fix glide path, a straight line to the runway. All you need to focus to is your speed, everything else is already done when you stabilize. This way, the pilot has the least possible stress during the landing. Follow the line, and watch the speed. No fancy maneuvers, no calculations. Keep the speed matching your waypoints and you are all right. Have a look to the queue of planes landing at the airport, doesn’t matter what type of plane is, they all follow exactly the same path.
There’s something called ‘slow flight’ on landing, the engines are revved up in case the plane needs to make a go-around (aborted landing), but with the shallow angle and flaps engaged it is moving slower. The runway is a pretty small target, so you want to make sure you’re landing with enough room for braking. If traveling steep and fast it’s easier to overshoot.
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