I don’t think you’ll get much mileage out of using the discrimination card against an airline. I’m guessing their argument would be that, although they place an age restriction on new applicants, it is only a restriction for a low hour entry and most companies could easily demonstrate that they employ a wide range of age of pilots (i.e. in easyjet I’m sure that there are loads of ex BA guys over 55).
When I was at my training school we had a talk from the recruitment guy from Jet2. He seemed really keen to take on older, second career type people. His argument was that because they only had 15-20 years of potential paid flying left, they were unlikely (well less likely) than a 20 year old to want to change companies when they had enough hours. The way he saw it was that employing older pilots was less of a financial risk to the company because they would work for the company longer and therefore reduce the impact of the initial training cost of a new pilot. (before anyone starts saying that you have to pay for your own type rating with Jet2 I’m talking about the extra costs of employing a low hour-ed pilot over a guy with 2000hrs on type, i.e. more line training to pass the final line check)
From what I’ve heard and seen, a lot of airlines seem to write off guys in their late 30’s, but it’s not the case with everyone. From what I can remember as well, FlyBe seemed to have the same attitude as Jet2. When I went to these talks was over a year ago, so things might have changed, but I’m sure that not all airlines are as short sighted as easyjet when it comes to age.