I had the same situation. I tried to take the ATP written before I turned 21 because I started applying for airlines when I was twenty and wanted to spice up the resume a little with the ATP written. I studyed and preped for it, went to the testing center, paid for ther test, and the test never showed up. We called and they said it would not come because I was not 21. I could not find anywhere in the regs where it said I have to be 21 to take the written. So I called the FISDO office and asked them. The were B***s**it at CATS. They told me that I can take the written no problem. So I called CATS they still said no. So I called the Feds again and they said they would look into it and called me back and told me to look under

61.35(a)(2)(iii) Date of birth of applicant must show that he or she will meet the age requirment for the certificate before the expiration of the knowledge test.