Unguided

Unguided, humans (and even animals!) inherently tend towards instability of motion.

This rings very true in flying

In 1926, the earliest days of instrument flying research, there were two military pilots, Major William C. Ocker- the 'Father of instrument Flying' and Lieutenant Carl J. Crane who developed some neat ways of troubleshooting the effects of loss of visual reference. The pair practiced blindfolding pilot peers and setting them about in a large area with the instruction to travel a straight course. Without fail, the test subjects demonstrated a perfectly imperfect spiraling trend time and time again. The tests were done while walking on foot, driving a jeep and operating a boat; with the same results each time.?

Being generally adventurous people, the two military aviators took it to another level: They captured a number of pigeons, blindfolded them, and released them from airplanes while cruising aloft. Now to me, that sounds like a rousing good time: (Science!)?

Read the result, quoted from their research:

"The pigeons without exception performed all manner of evolutions which indicated lack of flight control, including stalls and spiral dives. Finally holding their wings at a high dihedral angle, they descended to the ground in much the same manner as a parachute"

Even birds, who much more than humans are literally Made to fly rely so heavily on their visual senses that they become uncontrolled when losing that sense. Unlike the birds, a pilot cannot so easily settle to the ground again with their ship when giving up.?

We may think ourselves to be masters of the sky, but it's important to remember how infantile we still are when our modern adaptations fail us; or even our own eyes. How susceptible we are to disorientation!?

In a general sense this shows us to always respect the sky and the equipment we use in it. It can send us towards an untimely end the moment we lose focus or an error in instrumentation is encountered. In a specific sense, all pilots should be well-practiced in their Instrument proficiency, perception, and troubleshooting skills to properly return an aircraft to a state of control.?

On a large scale, the mistake has been made as recently as this decade, with disastrous results.?

The two aviators published their findings in 'Blind Flight in Theory and Practice' by Ocker and Crane, 1932.