airway vs skyway

airway

noun
  • A flight path used by aeroplanes. 

  • The trachea. 

skyway

noun
  • An airplane route. 

  • An elevated road. 

  • Synonym of skybridge: an elevated corridor connecting buildings above ground level. 

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