In the U.S., since there is not a Certified Flight Instructor (CFI) rating for "lighter-than-air" category pilots, someone who holds only a Commercial Balloon pilot certificate can provide the flight and ground training and various endorsements in order for someone to become a balloon pilot. 14 CFR 61.133(a)(2)(ii)(D)
Question:
Can the holder of a "Balloon" only Commercial Pilot certificate conduct and provide the endorsement for the 1 hour (minimum) of ground training required for a 14 CFR 61.56(a)(1) Flight Review for a pilot who holds, for example, an Airline Transport Pilot certificate and is only rated in Airplanes?
Of course the flight training portion of the Flight Review would have to be conducted by an instructor who holds an "Airplane" rating on his/her CFI.