I am 60 and am looking for a new job.How can I tell if an employer discrimates because of age. I feel they do

I have applied for jobs that I know I have more experience and better qualifications than the "younger person" they hired. They can't come out and say it is because of my age but I feel it is, but how can I prove it. They can use any reason they want and it is still "age discrimination". Don't they realize and older person in most cases are more reliable and dependable than the younger generation?