See also

External links

• "Night Flyers At 10,000 Feet Hurdle The Rockies", Popular Science
  Popular Science
  Popular Science is an American monthly magazine founded in 1872 carrying articles for the general reader on science and technology subjects. Popular Science has won over 58 awards, including the ASME awards for its journalistic excellence in both 2003 and 2004...
  
  , August 1931, article on early operation of Boeing 80
• "How Many Parts Has The Modern Airplane", Popular Mechanics
  Popular Mechanics
  Popular Mechanics is an American magazine first published January 11, 1902 by H. H. Windsor, and has been owned since 1958 by the Hearst Corporation...
  
  , January 1932, article on the parts and man hours in the construction of a Boeing Model 80