title: Number of classes in large projects
body: <p>I'm just wondering about large projects - say an airlines reservation system, how many classes/objects it is likely to have.  </p>
  
  <p>Objects: customer, airplane, airport, route, ticket, order.  That's about all I can think of.  The project will probably be hundreds of thousands of lines of code, so are there likely to be more classes (that do un-object related things)?  </p>
  
  <p>If so, how many classes are there likely to (roughly) be?  How many objects (as per my list so not 10,000 customer objects, how many different <em>names</em>) are there likely to be?</p>