air travel vs gliding

air travel

noun
  • Journeying through the sky, usually in an aeroplane. 

gliding

noun
  • The hobby, sport, or act of flying a glider. 

  • The action or motion of something that glides. 

adj
  • Employing flexitime. 

  • That moves or changes with a glide. 

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