Conversation so far:
what is a faa third class medical certificate?
A Third class medical certificate is appropriate for student pilots, recreational pilots, and private pilots who fly for pleasure or personal business.
how long is the FAA third class medical certificate valid for?
A third class medical is valid for 60 months for pilots under age 40, and 24 months for applicants who are age 40 or older.
what is a first class FAA medical certificate?
A first class medical is required for pilots who exercise airline transport pilot privileges

Question: what is a second class certificate?
Self-contained rewrite: what is a second class FAA medical certificate?