I have to agree - it will be several years before he will be picked up, if ever, if he doesn't stay current - which would be very expensive - likely to be good money after bad.
It's difficult to write off this size of investment, but most of us have lost this sort of sum at one time or other, especially recently. Airline flying ain't what it was anyway, and will be worse after c19. My advice would be to invest in training for a future proofed profession,eg IT. After a period of employment, there are some good government schemes which will provide and pay for this training