question: What were the people who used maps , blackboards , and mental calculation to ensure the safe separation of aircraft traveling between cities called ?
answer: air traffic controllers
turker_answer: air traffic controllers are the people who used maps , blackboards , and mental calculation to ensure the safe separation of aircraft traveling between cities called .
rule-based: The people who used maps , blackboards , and mental calculation to ensure the safe separation of aircraft traveling between cities called were air traffic controllers .