I brought this up in PhantomPilots. I'll copy that post below (it's long). Basically, IMHO they are all crap, can't be relied on and are incorrect. That is just the bottom line. The FAA's B4UFly app is terribly lacking and focuses mainly on any possible airport that might exist. No one can rely on that app alone. For example it does not even contain jails and prison's, where it's illegal to fly. I think DJI has probably done the best job. They are less obligated to give out NFZ info, have done so already and it's really the most correct.
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I don't see that anyone has really offered any type of solutions to the issue of avoiding NFZ. DJI's info is of little help and certainly the FAA is (still) falling WAY short of what they should be doing.
Let me start with DJI. I think they have done a good job when weighted against what they should be responsible for. They have built in many NFZ to their software. However, this pretty much only includes large airports and prisons. I personally think they have done a very good job in giving only warnings when near these locations and only shutting down the drone when it's about a miles away from the center of the location.
Who I fault most is the FAA. The actual tax paid entity that is charge of NFZ. Do this... search right now online for a searchable map of NFZ in the US. I have never been able to find one from the FAA. Please feel free to post here is you know where the FAA has this online. What they have done is put out a smartphone app (B4UFly). They can include a searchable map in a cell phone but not online?
We know for a fact that we can't trust the FAA's review of the actual laws governing UAV use... we always need to go directly to those regulations. Go to the FAA's website and try to actually find the regulations explaining why you need to call the airport. It will probably take awhile to find this information.
https://www.faa.gov/uas/media/Sec_331_336_UAS.pdf
The main part that applies is Section 336. I'll paste part of this below:
Now I could go on and on about the issues with the wording above but let me focus on one item... #5.
What is an "airport" as it applies to this entire section? It's not defined. You can find an explanation from the FAA in other areas of their website:
"An
airport is defined in the law as any area of land or water used or intended for landing or takeoff of aircraft including appurtenant area used or intended for
airport buildings, facilities, as well as rights of way together with the buildings and facilities."
So if the FAA chooses to follow their own information, you'd need to call anyone with anything that looks like could be used for a helicopter. So you'd need to include all helipads in the area. How many people call the local hospitals? If you do... PLEASE record that conversation as I'd love to hear their confusion.
Let me move in to the app....
If you look at the B4UFly app, it appears that the app almost agrees with this. That is, it seems to list most places that the FAA could know where aircraft can take off and land. This includes hospitals and small helipads. Other have commented on this (a fellow SLC flier recently)... if you were to go by the app, you may need to call a _lot_ of airports in order to fly in just one location. When I use a local zip code in the app, here is what was displayed:
If I were to follow the map above, I've be calling 9 hospitals and some crazy small "airport" (it's called "Number 18" on the map) to obtain permission to launch a drone 1" off the ground. Seriously? How do I call "Number 18"? Then, what is that huge red area? It seems that Salt Lake International Airport is within hat area (though, the circle for the airport appears cut off in the north east corner) but there is nothing else showing to state what that large red areas is. I also did a search for Lehi, UT which contains a prison. We all know you cannot fly over a prison. Guess what.... nothing on the map for that!
So this is what the FAA gives us so that we can know where we can and cannot fly. This not only does not really help, it makes the situation worse in many cases. This really only scratches the surface of how badly