Class E is the most common type of airspace in the United States, but it's often the least understood.

Class E Is Controlled, But How?

Class E airspace is controlled airspace. But why is it controlled?

In class E airspace, IFR aircraft are controlled by ATC. This might be a center facility (Air Route Traffic Control Center) or approach/departure facility. As a VFR aircraft, you aren't required to be in contact with ATC, but IFR aircraft must operate on an ATC clearance. That means the airspace is controlled.

Weather Requirements

Have you ever wondered why we have weather minimums? Imagine you're flying IFR and pop out of a cloud layer. Suddenly, you spot a VFR aircraft below. The VFR weather minimums give both of you enough time to see and avoid each other.

Here's what you need to fly VFR through Class E below 10,000 feet MSL:

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If you fly 10,000 feet MSL and above in Class E airspace, the weather minimums are raised:

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So, why do the requirements change at 10,000' MSL? Think about aircraft speed restrictions.

FAR 91.117 states that below 10,000 feet MSL, you cannot exceed 250 knots without a clearance. This helps separate slow flying traffic from larger, faster traffic by giving them more time to see and avoid each other.

Once you go above 10,000', speeds increase. So, to provide enough time to see and avoid aircraft, your weather minimums increase, too.

Class E Altitudes

The toughest part about Class E airspace may be recognizing where it starts. It seems to start at random altitudes all over the map, but there's logic to it.

Class E Enroute Airspace

You may have heard that Class E airspace starts at 14,500 feet, but if you look at the sectional, this often isn't the case. In the vast majority of areas, there are enough airports and victor airways to have Class E begin at 1,200 feet AGL. This is known as enroute Class E airspace.

On a sectional, it appears inside fuzzy blue borders:

Class E Transition Areas

In a Class E transition area, the Class E floor drops down to 700 feet AGL. On a sectional map, you can find these transition areas by looking for a broad, magenta line that is fuzzy on the inner side. It often surrounds individual airports or groups of airports.

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So why does the Class E airspace suddenly drop from 1,200 feet AGL to 700 feet AGL in these areas? Think of it like Class B or C airspace, it drops down to protect aircraft on approach or departure from an airport.

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You might ask, why would an IFR pilot be down at 700 feet miles away from the airport? Well, they wouldn't. In MVFR weather, you could have a VFR aircraft just a few hundred feet below an IFR aircraft in the clouds. These transition areas drop down low enough to separate IFR aircraft from VFR aircraft below.

Transition Area Shapes

OK, so Class E transition areas are just those magenta circles, right? Nope. You're going to find out there's a whole lot more to Class E than that.

In cases like the airspace image below, the airspace designer is taking into account the terrain elevation, as well as the amount and the types of aircraft using that airspace.

For larger, and faster planes, you need larger, more protective Class E transition areas. When you have rising terrain, the transition area must be larger to allow them to climb up to a safe en-route altitude.

Different Shapes

Some Class E airspace isn't circular, and many Class E transition areas have rectangular areas jutting off of the airspace. Why are they there? These extensions protect approaches and departures to and from airport runways. They also extend Class E airspace to protect aircraft transitioning into or out of airport areas from enroute waypoints such as VORs.

For instance, at Summersville Airport (KSXL) below, you can see the Class E extensions protect runway approach and departure procedures:

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At this airport, to comply with proper terrain avoidance, the protective Class E airspace has been extended in either direction. It's longer to the northeast due to rising terrain.

While confusing at first, once you know the logic behind the placement, it's easy to understand why it's there.

Class E Surface Areas

Class E surface areas look a lot like Class D airspace, but with a magenta border instead of blue:

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This is Class E airspace that extends down to the surface for and airport. It's nearly always surrounded by a Class E transition area, so the airspace mimics the wedding-cake shelves of Class C and B airspace. It's just a much less-controlled version of those types of airspace.

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Class E surface areas are often in place to protect precision instrument approaches. You'll also commonly find Class E surface areas with rectangular extensions for approach and departure procedures.

All airports with Class E surface areas are required to have a weather station and the ability for aircraft to contact ATC from the ground. In this case, ATC may include Flight Service, a center facility, or an approach/departure facility.

Putting It All Together

I remember when I was in flight training, I never thought about why Class E airspace was there, or the logic behind placement.

IFR traffic in Class E airspace is controlled by ATC, and the weather and speed restrictions make sure that IFR and VFR can see and avoid each other. While many of it's characteristics may seem arbitrary, it makes a lot of sense when you think how aircraft use the airspace.

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