I interviewed there recently, though decided to take another job. ITA uses Lisp for their core flight search engine, but uses other languages like Java and C++ for many of their other projects, such as the one mentioned in this announcement.
When I interviewed there in early 2010 they still used LISP. They said it was mostly because their hires fresh out of MIT wanted to use it, so I don't know whether they will continue to use it now that their MIT kids will no longer want to use it...
Scheme is no longer used in the introductory EECS course, but that doesn't mean there won't still be a lot of MIT grads hooked on the Lisp family of languages. (I think ITA uses Common Lisp.)
I imagine rewriting a large code base in any language to be very expensive, I doubt somebody can justify such an expense just because a bunch of new hires don't want to use a language. Companies don't rewrite java apps in lisp because a new of college grads don't want to use java.
I can't say i disagree with BigCo on this one. If one wishes to use better languages the options are to switch jobs, start your own company or stay, but push to augment the existing codebase with other JVM languages. Clojure and Scala people have had some success starting skunkworks projects. But a complete switch? In most cases thats insanity. Companies have actually died trying to rewrite their apps from scratch. And even a slow gradual rewrite might take too long and be too expensive, not to mention not bringing any immediate benefits, because you're not adding new functionality and fixing existing bugs.
