Age discriminination is when they
don't hire you because you are 40 or older.
Age Discrimination
If I was a CFO and counting pennies, and at my airline it was 10-years until Captain, hiring a 45 year old FO means I am paying FO pay for 10 years, then Captain pay for 10 years, then retirement. This carries over to the employee's health care costs, pension/401k matching, etc related costs.
If I hire a 25 year old, then I have 10 years as FO, then 30 years at Captain pay, that my airline has to pay out.
Remember, I just need a yoke monkey. Both guys may have the college degree, 3000 TT, 1000 turbine, etc yada yada. Now, what is best for my company ? the shareholder ?
Etc