Take a 90 year old (retired!) Spitfire pilot and member of The Few.
I have huge respect for him, but would I want him flying my family down to Spain? At what point does he change from Moustachioed Ace to Retired Hero? Would the authorities be able to determine the exact moment of when he had seen better days? Would it be fair on all other members of the profession for him to continue rather than freeing up the bottom rung of the ladder? Would he have been able to become the experienced pilot that he was if someone up the ladder had obstinately refused to make way?