With airlines I would generally recommend disclosing anything they ask for, but nothing more. The airline in question might be restricted by state law from asking as much as they would like...their loss, your gain.

It is often clear-cut, but if there appears to be a grey area I would recommend disclosure to be on the safe side. Only exception might be something which is so bad that you know they won't hire you if they find out...in that case you might not have much to lose by staying mum.