I can tell you as a Part 61 pilot, the FAA takes a very dim view of private planes below 500' as you are supposed to be 500' above any object, except in an emergency or landing/take off.
If you look at a sectional and see areas in yellow, those areas are heavily populated areas where you have to be at least 1000' above any object , so you are 1000'+ to be above buildings, trees, structures, etc
The exception is VR routes
As others have mentioned, the F-35 was probably in a Military Training Route which allows low-level, high-speed operations. Also, as has been mentioned in many forum posts, helicopters are explicitly exempted from the 500' minimum safe altitude as are all aircraft over water and in "sparsely populated areas" where the restriction becomes 500' from people or structures (not the ground). See (c) and (d) below.
Many times I have taken off from Furnace Creek airport (elevation -210' MSL) and cruised 50 miles down Death Valley with my altimeter displaying below zero, just because this is about the only place in the world where you can do that. This was before drones. If I were still flying today I would be scared to be flying anywhere below 1000' above ground level because of the threat of a drone strike.
As a drone pilot, I admit that there can be situations where, with the best of intentions and attempting to follow all of the rules, you can be surprised to find your drone in the same airspace as legally-flying manned aircraft. In our modern world accidents happen where everyone was following the law and no one was at fault. That doesn't make the consequences any less tragic. Everyone (manned and unmanned) needs to be extra-careful out there.
The regulation:
91.119 Minimum safe altitudes; general
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a)
Anywhere
– An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b)
Over 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.
(c)
Over other than congested areas
– An altitude of 500 feet above the surface except over open water or sparsely populated areas.
In that case, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
(d)
Helicopters
– Helicopters may be operated at less than the minimums prescribed In paragraph (b) or (c) of this section if the operation is conducted without hazard to persons or property on the surface.
In addition, each person operating a helicopter shall comply with routes or altitudes specifically prescribed for helicopters by the Administrator.