airplane vs helicopter

airplane

verb
  • To transport by aeroplane. 

  • To fly in an aeroplane. 

noun
  • A powered heavier-than-air aircraft with fixed wings. 

helicopter

verb
  • To transport by helicopter. 

  • To rotate like a helicopter blade. 

  • To overprotect one's children, as a helicopter parent does. 

  • To travel by helicopter. 

noun
  • A powered troweling machine with spinning blades used to spread concrete. 

  • A whirling trick performed with devil sticks. 

  • A dragonfly. 

  • The winged fruit of certain trees, such as ash, elm, and maple. 

  • An aircraft that is borne along by one or more sets of long rotating blades which allow it to hover, move in any direction including reverse, or land; and typically having a smaller set of blades on its tail that stabilize the aircraft. 

How often have the words airplane and helicopter occurred in a corpus of books? (source: Google Ngram Viewer )