Originally Posted by
Pilotpip
Not to mention that you are also exercising commercial pilot privileges if you're being compensated. Keep it at second class standing and you're fine.
I took mine on a second class which was 15 months or so old with no problem. This was where the above sentences come from as the inspector used this as a basis for our discussion on medicals. Your FSDO experience may vary.
You are not exercising commercial-level privileges while instructing. It is exempt from that...you do not need any medical to instruct, as long as the student can be the PIC. You do need a third class to take the checkride, since you will be PIC.
Some 141 schools may require a 2C for their instructors.