aircraft vs airship

aircraft

noun
  • A vehicle capable of atmospheric flight due to interaction with the air, such as buoyancy or lift 

airship

noun
  • A lighter-than-air aircraft that can be propelled forward through the air as well as steered. 

  • A police air unit, a police helicopter 

  • Any aircraft. 

  • A high ranking official of the RAF, viewed as arrogant and distant. 

verb
  • To transport goods by aircraft. 

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