§ 107.23 is the rule that catches everything the specific limits covered in § 1.2 do not — the 400-foot altitude ceiling, the 87-knot (100 mph) groundspeed cap, and the 3-statute-mile visibility minimum. You can comply with every one of those numbers and still break the law if you fly in a careless or reckless manner so as to endanger the life or property of another, or let something drop from your aircraft in a way that creates an undue hazard. It is deliberately open-ended — the FAA cannot write a rule for every dangerous decision a pilot might make, so this one exists to cover the judgment calls: buzzing a crowd for a better shot, flying distracted, pushing a damaged aircraft into the air. If an inspector or investigator can show your flight endangered someone, the specific numbers you followed elsewhere will not save you.

Two narrower rules govern where you can physically be when you fly, both found in § 107.25 (the rule on operating from a moving vehicle or aircraft). You may not operate a small unmanned aircraft system from a moving aircraft. Operating from a moving land or water-borne vehicle is allowed, but only over a sparsely populated area (a term the rule uses but does not itself define), and only if you are not using the flight to transport another person’s property for compensation or hire. Both conditions have to be true at once; a drone launched from a moving truck to deliver a paid package would fail the rule even in open country, because the vehicle is moving and the property is being carried for hire. Neither the moving-aircraft prohibition nor the moving-vehicle conditions are absolute in the way some Part 107 limits are, though: § 107.25 appears on the FAA’s list of regulations that can be waived, with one fixed exception — no waiver will ever be granted to allow carrying another person’s property for compensation or hire.

In the air, your drone is always the one that gives way. Under § 107.37, a small unmanned aircraft must yield the right of way to all aircraft, airborne vehicles, and launch and reentry vehicles — meaning it has to give way and may not pass over, under, or ahead of them unless well clear. A separate clause bars operating so close to another aircraft that a collision hazard is created, regardless of who technically had the right of way. Crewed aircraft are permitted to fly quite low in some circumstances, so a helicopter or low-altitude airplane can appear with little warning; the rule puts the entire burden of avoidance on the smaller, more maneuverable aircraft — yours.