airbus vs ramjet

airbus

noun
  • A subsonic jet airliner, especially a wide-bodied one. 

ramjet

noun
  • A jet engine in which forward motion forces air into an inlet, compressing it (as opposed to having a pump type device compressing the air for combustion with fuel), and where combustion is subsonic. 

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