If he’s planning to serve as PIC without a current medical or flight review, he’s breaking the law and he better pray he doesn’t get ramp checked by an FAA inspector. In addition, should he have an accident while doing this, he can be held civilly or criminally liable for whatever happens. This can include being sued for damages all the way to facing prison time for manslaughter, should his actions result in loss of life. It’s serious business.
Aside from the legal consequences of doing so, keep in mind that flying an airplane is a perishable skill and it degrades over time without regular practice. Add to that changing regulations and rules which you have to stay up to date with and you can get into big trouble in a hurry. Add into this cognitive deterioration which occurs as we age and it can become a real complication. I usually adviceadvise rusty pilots with whom I work with on their Biannual Flight Review (BFR) that a good rule of thumb is to expect approximately 1 hour of combined ground and flight training for every year that they have not been absent from being a pilot. You will be quickly amazed how much your skills can degrade over that time once you get back in hethe cockpit and assume PIC duties again.
This isn’t to say that it would be impossible for a 91 year old rusty pilot to get back into flying safely, legally, and reasonably. But it is going to be a commitment of time, money and effort to get this done right and return him to flying as a competent and safe pilot.
