Is this legal?

Have you ever been plotting along in your Cessna, Piper, Cirrus, Beechcraft, or Diamond and wondered, hey can I throw my bag of flour out the window and not be hunted down and killed by the FAA? I know I have. Just in case you were, I thought I'd clarify the Federal Aviation Regulations (FARs) on dropping objects from airplanes.

To most new pilot's surprise, it actually is legal to drop objects from your airplane... that is only if no property or person is damaged, maimed, or killed. So as I'm flying over the Allendale Columbia campus, I could drop a sack of flour onto the courtyard, as long as nothing is damaged and I don't hit anyone. Although I'm sure they could sue the bejesus out of me.

But you'd better have amazing aim or trig skills because you won't be able to fly very low. The FARs put the nail in the coffin for low-level flour bombing (at least in monitored areas). There are three regulations that make up the "minimum safe altitudes" rules.

Over congested areas: An altitude of at least 1000ft above the highest obstacle within a horizontal radius of 2000ft of the aircraft must be maintained over any congested area of a city, town, or settlement, or over any open-air assembly of people.

Over other than congested area: An altitude of 500ft above the surface must be maintained except over open water or sparsely populated areas. In that case, the aircraft may not be operated closer than 500ft to any person, vessel, vehicle, or structure.

General Anywhere Rule: The pilot must maintain an altitude which, in the event of an engine failure, will allow an emergency landing without undue hazard to persons or property on the surface.

The 500ft rule is the most important one when it comes to bombing anything, although the FAA could screw you with the Anywhere Rule anyway. Normally, flour bomb competitions (which happen quite often, as it is a major event at National Flight Team competitions) have the target on a closed runway, as there are no altitude restrictions set in stone (the anywhere rule is still applicable as long as the aircraft is not landing or taking off) over airports.

So in summary, yes dropping objects is legal, but it comes with a laundry list of ifs and buts. Of course you could just fly off the beaten path where there is no radar coverage and then obscure your aircraft registration so no one could report you.... but I won't never recommend or condone such actions. ;)