My past 12 months haven't been that lucritive (18 airports - ABQ BOS DEN FAT FRA IAD JFK LAX MIA NRT OAK ORD SBA SFO SJU SZG TPE YYZ - and ICN can be added on Saturday), but since you didn't restrict your question to commercial flights, my biggest year was 1993 with 41 airports - 3CM 6B6 ACK ARB ASH AYE BAF BED BFD BOS BVY CGF EWB FFO HDH HFD HPN HYA ISP LCI LEB LHR LWM MCO MHT MVY ORH OWD P10 PHX PSF PVD PWM SFO STL TLV TEB TLV TTN TUS YUM - only 6 of which were on commercial flights. My lifetime total is around 160, plus several off-airport locations...