Skyhawk 172/Cutlass 172
Flight Crew Private
Flight Crew Last 90 Days 40; Flight Crew Total 100; Flight Crew Type 95
Situational Awareness
Airspace Violation All Types; Deviation / Discrepancy - Procedural Security; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Exited Penetrated Airspace; General Police / Security Involved
Airspace Structure; Environment - Non Weather Related; Human Factors
I; along with 2 passengers; flew over and circled the fireworks show for 10-20 minutes. We entered the area at 3500 MSL adjusted for local altimeter. We then circled and descended to 2000 MSL over the area; watching the fireworks. Knowing [the airport's] field elevation was 1000 MSL; I thought to be within safe limits during the entire time. Using Foreflight and visual references; I noted there was no TFR over [the area] and that the location I circled was sparsely populated. I then descended to 1700 MSL with my final pass over the fireworks display and climbed to 2500 MSL departing back to the west; towards ZZZ. While circling the area; I noted there was other traffic in the area; as well as 5-6 drones circling the area. My radios were tuned to ZZZ's CTAF the entire time. I at no point felt I was being reckless or endangering anyone's life. I noted several open and unpopulated areas I could attempt to land at if my engine had failed. Two days later an FBI agent came to talk with me and asked if I was aware of a regulation that stated one could not fly below 3000 AGL over a crowd of 10000 people or more. I informed him that I wasn't aware of any such FAR and he informed me it was not a FAR but a DHS regulation and that my act could be conceived as terrorism. I told him everything to my knowledge what had happened and that I did not go below 500 AGL because I deemed it to be a sparsely populated area. From the air; I and anyone flying that night would have been unable to determine that it was a densely populated area or that there was a crowd of 10000 or more people. This situation can possibly be avoided in the future if a TFR were to be set up during the time of the firework display. That way all future operators and pilots would know not to descend below 3000 AGL. If in the future there were to be no TFR; I see how no one would know not to descend as low as I did.
Cessna 172 pilot reported flying below 3;000 feet over a crowd of 10;000 people or more; claiming no TFR was published.