flew with their ears
... that airline pilots in the 1930s and 1940s flew with their ears when visibility was poor?
... that <a class="mw-redirect" href="./Aviator" id="mwA_Y" rel="mw:WikiLink" title="Aviator">airline pilots</a> in the 1930s and 1940s <b id="mwA_c"><a class="mw-redirect" href="./Low_frequency_radio_range" id="mwA_g" rel="mw:WikiLink" title="Low frequency radio range">flew with their ears</a></b> when <a href="./Instrument_meteorological_conditions" id="mwA_k" rel="mw:WikiLink" title="Instrument meteorological conditions">visibility was poor</a>?