FAR 103.15 states:

No person may operate an ultralight vehicle over any congested area of a city, town, or settlement, or over any open air assembly of persons.

I'm wondering what is meant by "congested area". It sounds like you can fly over a city, town or settlement so long as it's not congested but...how is that defined?


I could not find a definite definition of congested area.

As mentioned here:

[...] neither the FAA nor the NTSB has ever provided [...] a precise definition of [...] a "congested area." Rather, a "congested area" is determined on a case-by-case basis. According to the Board, "the determination must take into consideration all circumstances, not only the size of an area and the number of homes or structures, but, for example, whether the buildings are occupied or people are otherwise present, such as on roads."

The same is echoed here:

[For the definition of congested area,] FAA and the NTSB have opted for taking a "case-by-case" approach in determining how to apply certain terms.

AOPA states that:

Congested areas. "Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft." The FAA does not define congested area in the FARs or in the Aeronautical Information Manual. Interpretations in low-flight enforcement cases are not consistent for purposes of drafting a precise definition. Such a determination is usually decided on a case-by-case basis, and in the cases that we've seen, congested has been interpreted rather broadly. For example, a highway with moderate traffic was found to be "congested," as was a seaside area where 200 to 300 persons were sitting on the beach or bathing in the water.

The same can be seen here, and here, and here.

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    $\begingroup$ This makes sense. After all a county fairground, 355 days a year may be an empty field... but for a few days...it's definitively congested. $\endgroup$ – CGCampbell Jun 9 '15 at 20:42
  • $\begingroup$ Is it basically only being defined when there is an incident that is being investigated? IE., aside from an obvious breach, you probably won't hear much about it unless there is some sort of complaint leveled against your flight path (or you have an accident, etc.)? $\endgroup$ – Jay Carr Jun 9 '15 at 20:46
  • $\begingroup$ @JayCarr Not only in case of a breach. The AOPA definition (above) sort of answers your question. I think insurance companies might have more guidelines. $\endgroup$ – Farhan Jun 9 '15 at 20:50
  • $\begingroup$ Huh, I guess the moral for ultralights is to just stay away from people as best as humanly possible. $\endgroup$ – Jay Carr Jun 9 '15 at 21:14
  • $\begingroup$ How did a pilot measures 2000m AGL? Normally we measured ASL, as it normally done by any measurements. $\endgroup$ – AirCraft Lover Dec 29 '18 at 4:00

It is not explicitly defined in the FAR Definitions and it seems the explicitly do not define it.

I would interpret (please keep in mind this is my interpretation and not law) a congested area/assembly of people, as anywhere you could not safely land the aircraft in the event of an emergency without endangering others and or yourself. This may better by explained with an example.

Lets say you are flying low over main street at rush hour, your engine goes and you are forced to make an emergency landing. You have limited distance and direction to go and can not safely land the aircraft with out hitting either a building, people or vehicles on the road thus endangering them.

With that being said, you are correct that class B generally lies around the big cities in this country, and other cities may reside in class C, you can still have a congested area or open assembly of people (concert, state fare etc) in class G airspace.

  • $\begingroup$ Actually, everything I'm reading says that the FAA very specifically does not have an explicit definition of "congested". Not sure why, but they refuse to define it and, thus far, no real pattern has emerged from the rulings regarding the term. So it remains emphatically undefined. $\endgroup$ – Jay Carr Jun 9 '15 at 21:13
  • $\begingroup$ I provided my definition as what I feel a congested area is and what would be a safe bet to use when making your own decisions. I see that the FAA takes it on a case by case situation but that means that its up to you to define and you should build your own definition as best you can to avoid being in the situation where they need to investigate it. $\endgroup$ – Dave Jun 10 '15 at 14:34
  • $\begingroup$ I'd agree, and on the whole your answer adds a lot to the conversation, I just disagree with the second clause of your first sentence, that's all. There is no explicit definition in this context. But yes, you should do your best to create an internal definition to hopefully stay out of any situation where the FAAs definition (whatever it may be) actually matters. And you've done that here. It was surprisingly difficult to choose between the answers, I went with the other because of it's citations mainly. $\endgroup$ – Jay Carr Jun 10 '15 at 17:46
  • $\begingroup$ Ahh i see what you are referencing, I was hesitant to say it was or was not defined when I researched it as I had not found anything but I will edit it to reflect what seems to be the case. $\endgroup$ – Dave Jun 10 '15 at 18:47
  • $\begingroup$ Awesome, and again, I really did appreciate your answer. It's another one of those cases where I wish I could combine a couple answers into one... $\endgroup$ – Jay Carr Jun 10 '15 at 23:39

If a regulatory authority does not define the word, then by default it is the common definition of the word. Un-congested vs congested. Think of the phrase Open space and occupied space. If flying over occupied homes or businesses it is by definition congested. If you are flying over open land it is un-congested. In reality, the FAA uses many words and phrases with out providing what their definition is and leaves it to the common understanding rather than a unique definition. Simple English...but not to those who push the limits.


While getting my Aerospace Engineering degree a "Regulations and Legal Interpretations" class was mandatory. As part of that we studied cases against pilots such as flying low over farm houses. The judges have been persuaded to accept 2 or more people as "Congested" or an "assembly" based on existing automobile traffic laws that fines people for violating speed limits for crowds or people (plural). For example, "when children (pl 2 or more) are present".

Take this at face value. I don't agree with it but it seems to be a case where the Government feels more successful by being vague then being reasonable. To me something like "more than 25 people in a 1 mile radius" would be more quantifiable.


You can fly over a city which is congested, by following railroad tracks, etc, those areas are uncontested. But, you must be in class E or G airspace, unless you have clearance from the controlling agency.

The FAR 103.11(b) is only for flying with strobes, during civil twilight. You must be in uncontrolled airspace, which is class G, generally, but not always, starting at 700 or 1200 feet AGL.

Where I live ..0-500 feet is class G and class B starts at 500' ago. So I could fly my ultralight at 400', 20 minutes after sunset, along railroad tracks thru a major city.

A bad decision is called pilot error, your job is to keep others safe from your stupidity. :)

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    $\begingroup$ Welcome to Aviation.SE! I removed the large image from your post, since it was not relevant to the answer. I was also wondering if you have a source that confirms that railroad tracks are not considered congested areas? $\endgroup$ – Sanchises Oct 24 '18 at 8:29

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