Originally Posted by
PaoCM
I was most grateful to Copa counter personnel at SJO who warned me if I flew to Perú from Costa Rica that I didn't need the yellow fever certificate, but without one I could not board to come home to Costa Rica (yes copa, counter staff in Lima did ask!)
YMMV, I fly this route three times a month and have never been asked for YF certificate either at SJO/PTY/LIM, although I do carry one. AV from SAL is the same, never been asked.