Part 2: What is Airspace?

In this next installment of Airspace and Flight Procedure Development, we’ll focus on
defining: What is Airspace. This is important to address this topic before we delve into a
historical view of airspace and flight developments and before we discuss how these are
addressed today.

Have you ever looked above you and thought: What a beautiful, clear sky? I think we
have all done this where we admire cloud formations, geographic features, endless lakes
and oceans, and other features surrounding us. From an aviation perspective, wide open
expanses are often how the airspace above our heads is considered, however, the reality is
significantly different.

Prior to 1946, there was a common law which stated a person whom owns a plot of land,
also owns the sky above it. Enter Mr. Causby, owner of a chicken farm in a field next to
where the military placed a new airfield. The aircraft on approach to the runways were
literally scaring his chickens to death, causing Mr. Causby great financial harm. Citing
the common law, he filed suit against the government claiming ownership of the air
above him. The government countered citing the 1926 Air Commerce Act. Seeking a
final remedy, the United States Supreme Court handed down a landmark ruling favoring
the Commerce Act and ending this ownership of the airspace above a property owner.
This ruling gave rise to the Civil Aeronautics Authority (CAA) which eventually became
the Federal Aviation Administration (FAA).

As air commerce has grown the ability to manage the traffic within has become more and
more complex. Thus, the FAA has divided the airspace into “sectors” that assist Air
Traffic Control (ATC) in the management of this traffic. These sectors are defined by
lateral and vertical boundaries. For example, a sector may extend for 20 miles
horizontally and vertically for 10,000’ with other sectors surrounding it on all sides as
well as above and below. Figure 1 below is an overview of the Los Angeles Class B
airspace (NOTE: The FAA designates “classes” of airspace based on their overall usage.
The discussion here about sectors is independent of the classes of airspace. We are not
addressing classes of airspace here.) This diagram shows a top down view of the overall
airspace lateral boundaries. Within each boundary there are altitude limits drawn that
look like 100/50. This means that parcel of airspace, within those lateral boundaries,
extends from 10,000’ to 5,000’ above the ground. Below, above, and adjacent to those
altitudes are other sectors of airspace.

Figure 1. Los Angeles Class B Airspace Overview. A full image can be found here:

This stratification of airspace exists all over the world with certain locations being more sectorized than others based on traffic flow. Air traffic patterns/flows, can change over time through a modification process that involves negotiations between the sectors impacted by the desired change. Reasons for a sector boundary change may include safety reasons, traffic flow, new flight procedures, or other such occurrences.  When a change needs to be made to an existing sector, the Air Traffic Control (ATC) group that controls that sector will approach the adjacent ATC sector and begin a process of working out how changes can be made and assessing what the impact will be to the overall structure beyond these two sectors in discussion. This process is not instantaneous and must proceed through a well-documented FAA process before a final amendment can be made. This last point is very important to consider when someone looks at a map and says: Why don’t we just move the flight pattern over to this new location?  Airspace is not that simple.

Finally, if the image above seems confusing, that is because it is. Now, go back outside, take a look up at the sky above you and picture this stratification. Sectors of airspace surround you and are closely monitored by ATC and the FAA. Changes can occur, but must address many surrounding issues and stakeholders, such as airports, airlines and the surrounding community to name a few, in the process. As we continue this series, this process will be central to our discussions.