A CFI on my field asked me to ride along with him on a new students' first ride using my doctor brain - not my older-than-dirt' pilot brain that I am so proud of... "and keep your trap shut."
The student was a fella in his early 60's... Had some 104 hours of flight training and had still not been signed off for a check ride... He believed all his previous CFI(s) had been milking him (seems he made a point of making sure everyone knew he had "money")
Anyway, the guy was pleasant, seemed mentally capable, and so after an hour and a half of mini ground school where he was able to recite the usual stuff that makes up ground school (I said nothing) we went flying...
The CFI wanted to measure him up and with 104 hours in the log did not feel he needed to do the first flight show and tell routine... So he asks the student to demonstrate a soft field takeoff... The guy promptly puts on full flaps and starts to enter the runway - the CFI aborts that...
OK, so we make a 180, do a bit of show and tell on how you match the flap travel to the aileron travel, etc... Talked about trim setting - yadda, yadda, usual stuff...
(I of course said nothing - the CFI said to me later that he thought at that point that the guy was right, he had been fleeced)
So we do a somewhat drunken version of a soft field takeoff... Then we go out and do some slow flight, a stall, a couple of steep turns... He handles the plane marginally at best, sloppy turns, no altitude control at all, and doesn't seem up to the 104 hours of dual he logged...
The CFI sits there with his arms folded and says lets go back and shoot a couple of landings...
First the guy does not know how to find the field (well, OK it is a strange field but it is right there almost dead ahead 5 miles - no situational awareness)... So we go through how you look on the chart, find the NDB frequency and dial it in...
Then the guy goes screaming across the field 500 feet off the ground and turns steeply onto a right hand base for the downwind runway! No downwind pattern entry, no checking the sock, and he flushed two airplanes out of the pattern like startled chickadees...
The CFI says "my airplane" takes it and makes the corrections, uses the radio to sooth some ruffled feathers, and lands... He tells the student to put the plane in the hangar... While that is going on he looks at me...
I shrug and say basically the same as above; there is a cognitive defect... He is smart and can memorize and recite abstract ideas, but he is the guy who walks out of the store without paying, turns left in front of oncoming traffic, in a social situation cuts other people off in mid speech, and can never find his car keys... Putting him into a solo airplane is a death sentence - for someone...
Some people cannot be allowed to fly...