Let's say, there is a strange loud noise coming from a speck in the sky above a meadow in a national park: while watching it, it turns out to be a model plane making circles around a meadow taking pictures.
It was a drone, an aircraft without a pilot and is operated by remote control, flying above the meadow getting closer and closer : flashing lights, motor making noise, and the noise seems to be dragging, in other words out of sync.
The drone was taking pictures of the meadow, where you are sitting quietly watching a mother bear taking a nap and several of her cubs playing.
Tourist at at Alcatraz complained, in the past, that a drone was flying so close they could not hear the park ranger, who was giving the tour. Later, the drone got to close to the people taking the tour that they got scared: The park rangers traced the drone to a boat in the bay.
In Yosemite they ban drones and model airplanes so that they would not bother mountain climbers, hikers, and the tourist walking around on the park trails. Many of these drones can get out of control by updrafts and down drafts between the mountains and have crashed, according to several controllers, who fly drones in case of fires and rescue searches.
An experience controller, for the army, said that after the drone he was controlling crashed into an airplane, he felt so guilty, that he could not handle drones anymore and had to switch to another field in the army..
Because of incidents similar to these, in the near future, drones and model airplanes will be ban from many national parks, according to Park Service Director, Jonathan Jarvis: fire fighting, research, and rescue drones will be excluded from the ban.