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With how many planes there are in the sky flying at the same time, it’s a miracle there aren’t more accidents. So where do planes intersect?

Planes are able to intersect thanks to required separation between aircraft while flying. Separation minima is first addressed in the vertical direction to keep planes between 1,000 and 2,000 feet from one another. If vertical separation isn’t applied, then aircraft must be separated horizontally.

There are tens of thousands of flights every single day across the globe, and it takes expert coordination to avoid accidents. That said, planes still need to be able to intersect paths to get to their destinations. In this article, we’ll take a look at where planes intersect in the sky, how they do it, what separation between aircraft is required to be, and more.

At SkyTough, we want to provide you with only the best, most accurate aviation content that you’ll find on the web. In addition to our own knowledge and experience, we combined extensive research and discussion with other experts in the field. This way, we can get the full picture to you so that when you’re done reading, you will know exactly where and how planes intersect.

Table of contents


How Do Planes Intersect While Flying?

If you look up at the sky at any given time, it looks like there is just endless space up there. With how much room there is in the air for planes to fly, it seems like there is no way that two planes could ever intersect with each other. After all, there can’t possibly be that many flights where too many planes will be in the air at the same time, right?

Not quite. The fact is that there are roughly 100,000 flights that take off and land around the world per day. To give you an even better idea of how congested the world’s airspace might be, it’s estimated that there are nearly 10,000 planes in the air on any given day, no matter if it’s day or night. That’s quite a few planes up there that need to be able to safely reach their destinations!

So how and where do planes intersect?

The short answer is that planes are able to have intersecting flight paths in the sky thanks to minimum separation between aircrafts that is required at all times. In aviation, separation refers to minimum spacing between two aircraft and is implemented to prevent collisions and accidents while flying.

The long answer is a bit more involved, so let’s break it down and dive in a little deeper.

Do All Planes Fly At The Same Altitudes?

The first part of understanding how planes are able to intersect is knowing the heights at which planes fly. Of course, different types of planes fly at different altitudes, but the vast majority of planes — particularly commercial planes — fly at roughly the same altitude. This is because due to how planes fly, it’s best to operate within the layer of the atmosphere known as the stratosphere.

Planes fly within this layer of the atmosphere for a number of reasons. These include improved fuel efficiency through reduced drag, avoiding weather, less air traffic, and more. If you want much more detailed information about where planes fly in the sky and why, check out our full article on the subject.

But the important thing to note here, is that one of the reasons is to avoid air traffic. This is of note because most smaller aircraft such as single engine planes, helicopters, drones, and gliders all operate at lower altitudes. So these types of aircraft typically don’t have to be accounted for while planning flight paths and worrying about intersections.

So the important thing for airplanes flying within the stratosphere is that they maintain minimum separation to avoid potential disaster.

What Is Separation Between Aircraft?

When it comes to the aviation industry, separation is a concept utilized by air traffic control (ATC) to reduce the chance of having mid-air collisions and accidents due to other things like wake turbulence. In layman’s terms, this just means that separation is the required minimum distance between any two aircraft that are in the air at the same time.

By keeping planes a certain distance away from each other, the chance of them colliding is less than if the relative distances were not monitored. Since it’s impossible to apply separation to all aircraft in the air at the same time — and also entirely unnecessary — it’s only applied to planes that will be flying similar flight paths.

This is because any two intersecting flight paths have to intersect at some point no matter what. So separation is necessary to ensure that any planes on intersecting paths will not actually ever come close enough to collide. This is most easily done using vertical separation, but horizontal separation can also be applied if necessary.

Vertical Separation In Aviation

Most commonly, planes are kept from colliding with one another thanks to vertical separation. As the name implies, this is the distance that planes are required to be away from one another in the vertical (up/down) direction once separation is applied to them. Vertical separation is applied as follows:

*Applies only to airspace where RVSM can be applied

From the table above, you can see that the general trend is that as altitude gets higher, the required separation gets greater. This is because in most cases, especially for aircraft with older altimeter equipment and autopilot systems, altitude accuracy gets less accurate as air density lessens. So there needs to be more room for error the higher the planes are flying.

Also, be sure to pay attention to the note under the table. RVSM refers to Reduced Vertical Separation Minima. This is in reference to the fact that aircraft with more modern equipment are able to keep only 1,000 feet of separation at heights up to 41,000 feet (FL410) since it’s accurate enough to accurately monitor altitude at these heights. RVSM airspace includes:

  • North America
  • Europe
  • Asia (parts of it)
  • Africa (parts of it)
  • Pacific Ocean
  • Atlantic Ocean

Also of note with intersecting planes and vertical separation is minima is why it’s mandatory for pilots to turn on the autopilot system once they reach an altitude of 29,000 feet or higher. This is because modern autopilot systems are able to keep planes at a consistent altitude more accurately than pilots are able to on their own. So no matter how much hand flying a pilot wants to do, autopilot is mandatory at these heights!

Horizontal Separation In Aviation

As mentioned above, vertical separation is the most commonly used tactic to allow planes to intersect paths while flying. But sometimes, vertical separation is either not possible or is not capable of being maintained for one reason or another. In these cases, some type of horizontal separation must be used by ATC to prevent issues caused by intersecting planes and flight paths.

Procedural Separation

Procedural separation is used when the separation between two aircraft is designated by the aircraft’s position rather than certified radar. The first type is lateral separation, in which planes must be separated based on a certain distance from a common radio beacon. The second type, longitudinal separation, follows the 10-minute rule. This rule insinuates that no two planes on the same path may fly within 10 minutes of each other.

Radar Separation

As the name suggests, the second major type of horizontal separation uses certified radar that has been suitably calibrated to accurately show separation distances between aircraft. The distances allowed are published by the Federal Aviation Administration (FAA) and typically range anywhere from 3NM to 10NM.

In the end, separation is the key to allowing planes to intersect in the sky. Without separation minima, planes could potentially be flying at the same altitude while on intersecting paths. And you imagine the kind of devastation that could potentially stem from that.