Airspace is classified according to a lettering system. Even though we are not allowed into Classes A, B, C, D, Restricted or Prohibited Areas, we are allowed into nearly all of Class E and all of Class G airspace. (as per FAR 103)

Many of the images in this article link to the website skyvector.com. This is a great resource that can used to look up info for a flying trip to a new region. You need to know where the areas are that you can and cannot fly, especially on XC flights. One of the keys to using sectional maps is to get familiar with the legend area of the chart. Once you start to get a feel for each of the symbols and the purpose of the divisions of airspace, looking at a sectional can begin to become a little fun.

NOTE: Each image below links to sky vector and will open in a fresh tab or window. This way you can go play, then close the tab or window and continue with the article.

Below is an image of the legend area of a sectional chart. You can see the line colors and types that denote how the airspace is designated in the sectional. As you read this, break-out and look at the charts. Start with the legend area and go back there if you see any symbols or boundaries you do not understand.

Legend Area (Click to view full size – separate tab)

The Federal Aviation Administration is the federal agency responsible to regulate aviation within the US. Most hang gliders meet the requirements to operate as unpowered ultralight vehicles and as such benefit from having very little in the way of regulations to follow. Along with not needing aircraft inspections or licenses to fly them, we are allowed to fly in most areas. Learn more about the FAA.

Class A Airspace:

Class A airspace is not shown on your sectional. It covers the entire nation, so all we have to remember is that its lower limit is 18,000 MSL (mean sea level).

The term “controlled airspace,” by the way, doesn’t mean that somebody or some agency is up there controlling traffic, but controllers have a pretty good idea of what is up there. Use of our national air traffic control (ATC) service is mandatory in Class A airspace that begins at 18,000 feet MSL and extends upward to 60,000 feet MSL.

Altitudes at 18,000 feet MSL and above, in Class A airspace, are commonly referred to in hundreds of feet as “Flight Levels,” abbreviated FL.

For example:

• FL 200 (“flight level two zero zero”) = 20,000 feet MSL
• FL 600 = 60,000 feet MSL, etc.

The United States, of course, does not own or control airspace outside its territorial limits, but our government has extended Class A airspace out to twelve miles from the coast of the contiguous 48 states and Alaska. By the way, if you fly into Mexico or Canada, or if you want to rent an ultralight overseas, do not assume that you understand their airspace system. It will be similar, but homework is required.

Memory aid: Class A airspace = Above, as in 18,000 and Above, as in high Above everything else.

Class B Airspace:

Class B airspace surrounds the nation’s busiest airports and usually goes as high as 10,000 feet MSL, in some cases even higher. The uppermost level of Class B airspace may extend horizontally with radius of up to a 15 nautical miles around the airport tower. There is, however, no universal set of Class B dimensions since the flow of traffic, geography and other considerations determine the exact architecture of each Class B area. A sectional or a VFR Terminal Area Chart is very helpful in understanding the design and lateral dimensions of each Class B airspace.

Theoretically, an ultralight might fly above Class B airspace, but that could be extremely dangerous. Besides, you might be flying over a congested ground area and, in certain areas, through relatively congested airspace as other aircraft are funneled through narrow approach and departure routes.

On your sectional, horizontal Class B airspace limits are outlined in concentric solid blue circular lines that may be indented or extended in certain places due to geography or air traffic routes. The top and bottom of each layer of airspace, as you can see, are given in what looks like a fraction; for example, 90/40.

That means that this particular layer of airspace lies between 9,000 and 4,000 feet MSL. (SFC stands for surface) A two dimensional sectional map can only show you the horizontal outlines of different layers, you have to use the fractions to visualize the vertical dimensions. If it helps, close your eyes and try to “see” the architecture of the different layers. If you try to think in pictures rather than in words, that may help. Imagine an “inverted wedding cake.” with at least three layers.

Please notice the Sailplane icon with an H in a diamond above it, on the left of the below image. This represents the local Hang Gliding and Paragliding activity at Mussel Rock and Fort Funston. More important is that the innermost ring of Class B airspace for SFO has a subsection (blue line that goes inside of the 100/SFC ring). This is called a “keyhole” and this one shows that in this area, the base of the Class B airspace is 1600′ (100/16) instead of the SFC that is designated for the rest of the inner area. The keyhole is the triangular area just to the right of the red circle around the 100/16 notation. If this keyhole did not exist, we would not be able to fly hang gliders or paragliders in this area, as the default class B circle goes to the surface.  South of the keyhole, just north of  Sharp Park, the class B airspace window is in the 100/21 notation.   This means that in that area, it is a bit more lenient and the ceiling for ultralight craft is 2100 feet.   North of  the Westlake cliffs, the ceiling also rises, briefly, to 2100 until around the Stable flying site and then raises to 3000 feet heading North.

Wind Shears Warning:   In normal flying, it is almost impossible to ascend above the 1600 foot ceiling at Mussel Rock.   Wind Shears can change this.   Please read the linked article to learn about these patterns.   If you are skilled enough to leverage a wind shear, please make sure you move south or north “BEFORE” there is any chance of going above the 1600 foot ceiling at Mussel Rock and the keyhole area.  Flying in shears is for pilots with experience and not for newer pilots.

Check your sectional and you will find that the surface area of a city lying in Class B airspace is colored yellow as are all cities on the sectional. Obviously, this is what the FAA would call “congested” area, and ultralights may not fly over congested areas even if they were not in Class B or other controlled airspace. Visual clues and good judgment are your best guides for avoiding ground congestion. Even though ultralights are not permitted in class B airspace without prior permission, some operators have reported that ATC has granted permission for individual flights.

Many of the fields and airparks where ultralights fly are under overhanging layers of Class B airspace. If they fly too high, or if they fly just above the surface toward a major city airport, the ultralight will penetrate the Class B airspace, and that may set off lots of alarm bells with the FAA. The inner circle of Class B airspace extends all the way to the surface.

If you fly from a field that is under or near Class B airspace, you should study your sectional or Terminal Area Chart (TAC) to memorize landmarks that might help you recognize the locations and altitudes of various sections of Class B space.

In your memory, let B stand for Big Airport.

Class C Airspace:

On your sectional, horizontal Class C limits are shown by solid magenta lines. It is similar in layout to Class B but in magenta not blue. Altitude fractions show the upper and lower vertical limits as they do with Class B. As with the shelves of Class B airspace, you may fly under or over shelves of Class C airspace, but never into the airspace itself.

The below picture depicts “Norm Minetta” – San Jose International Airport (Class C airport) – note that the airspace lines around it are magenta, not blue as the above SFO “B Class”

If “B” stands for “Big Cities,” let “C” simply stand for Commercial Airports. The airports under class C airspace are mostly at mid-sized airports, but can also be the secondary airport in a major city.

Class D Airspace:

Small city airports with control towers are usually designated as Class D airspace. Associate “D” with “Dinky” or “Dime-sized” airports if you like, and do not go there without permission either. Commercial and other IFR traffic may be flying into these fields, and there is often much general aviation activity and pilot training.

The ceiling of Class D airspace generally extends upward to 2,500 feet AGL over the airport surface but the exact upper limit is shown with a number inside a dashed box outline.

Below is a sample of a “Class D” airport, Livermore, CA. The ceiling of the airspace at this airport is 2,900 ft MSL as is noted in the [29] box.

Flying over Class D airspace may not pose problems for the experienced ultralighter unless it violates the rule that ultralights must avoid flying over congested areas on the ground.

Class E Airspace:

Controlled airspace is officially defined by exclusion, which often does not tell you much. By that reasoning, Class E airspace is controlled airspace that is not Class A, B, C or D or G (explained below) airspace.

“Surface Class E,” is indicated by dashed magenta lines around the airport as shown below. Inside the dashed magenta line, the floor goes all the way to the surface.

Notice in the below image that this airport looks like a Class D airspace, but that it is magenta, not blue. This indicates only that the Class E (Controlled Airspace) drops below the default altitude limit for the area and instead goes to the ground.

Class E almost always has one of four lower limits: surface, 700′ AGL, 1200′ AGL or 14,500′ AGL. Most of the country has a Class E lower limit of 1200′ AGL.

In the below photo/link, the blue circle defines that inside the circular boundary, the controlled airspace drops to 1,200′ agl, and outside the circle, the controlled is 14,500 msl.

Occasionally the floor of Class E is none of the usual values. Where it is a discrete value it is shown by a staggered blue line.

The below image shows a line that depicts areas where the base level for the controlled airspace is well above 700′ and is different on each side of the offset division line.

Class G airspace:

Think of Class G as “ground” airspace. It covers almost the entire country. In very remote areas it has an upper limit at 14,500′ msl. However the vast majority of area of the country it has an upper limit that follows the contour of the ground.

Ultralight craft can fly in Class E and Class G airspace, the difference to us directly is that the cloud clearances are slightly different.

Memory Tools for Classes of Airspace:

• Class A think –> “above 18K”
• B think –> “Big”
• C think –> “Commercial” or “City”
• D think –> “Dinky” or “Dime Sized”
• E think –> “Everywhere”
• G think –> “Ground” or “Ground Proximity”

Special Use Airspace:

Restricted and Prohibited airspace look the same on a Sectional chart. The perimeter of the areas have a solid blue line with hash marks inside.

Restricted Area — A restricted area may be quite large. The image below shows some Restricted Areas and also contains some MOA areas (they look similar, but are magenta instead of blue). Notice that restricted areas are clearly marked with restricted within the boundaries.

Prohibited Area — A prohibited area will look the same as a restricted area, but will be clearly marked with the words “Prohibited Area” on your sectional.

These prohibited areas involve national security and sometimes environmental protection. They are not to be ignored under any circumstances.

Victor Airway — A Victor Airway is a special kind of Class E airspace.

We are allowed to fly there but it’s a good idea to know where they are and avoid them if you wish to reduce the amount of air traffic you are flying in. Victor Airways are like highways in the sky.

Below is the area near the flying site, Slide Mountain. The faint blue lines in this area represent two Victor Airways. They are named V 28-113 and V 994. Also note that there are two sailplane symbols, one with an <H> (signifies Hang Gliding and/or Paragliding – Ultralights in area) above and the other with a <U> (signifies Ultralight in this area). The one with the hang glider symbol is near the Slide Mountain site. (The Victor Airways are close to the Slide Mountain flying site, so awareness of them is a good idea.)

Military Training Routes — MTRs are depicted as thin, light gray lines on the sectional. Each has its own identification, and the identifier has two parts. “VR” means that pilots flying the training routes will be flying under visual flight rules. “IR” means the pilots will be flying under instrument flight rules.

Warning Area — This is a hazardous area that lies over international waters, beyond the three mile coastal limit.

Military Operations Area (MOA) — These large areas of the country are shown on your sectional as enclosed by a line of magenta hash marks with a sharp outer edge.

Alert Area — Bordered the same as a Restricted and Prohibited area, the identifier is not with a R or P but with an A. We are allowed into Alert Area without prior permission.

Things Change / TFR (Temporary Flight Restrictions) — Presidents and other important people who require high security show up everywhere from time to time, air shows open and close, natural disasters suddenly command attention, runways close for repairs, etc. Be aware of current events in your area.

TESTING – New Quiz – Please feel free to try this, in development.