Years ago I flew for a company (a predecessor of Ryanair but UK registered) with a Rombac BAC 1-11 which was fitted with 102 seats and therefore needed three cabin crew. Occasionally we ended up short of that number and a bright spark suggested that if we took out the last row of three seats we would be legal with only two cc. Initially this worked well until our flight ops inspector ruled against it saying that they had been trained to work as a three woman team and by reducing to two safety was compromised. The rule stated that the number of pax was irrelevant. What mattered was the number of seats and the crew had to match that. And in our case we couldn't just reduce the number of seats on an adhoc basis without a full cabin crew retraining course.