ITA software is an acquisition, and I’m sure most of the Lisp development at Google is just done by engineers tweaking their .emacs files.

The problem of parsing data from airlines is fiendishly hard. There are a ton of different rules for how to calculate prices, and all sorts of deals and promotions that may affect a particular route on a particular day. If you have a system which can parse this data, then you wouldn’t want to rewrite it. I’ve read a number of articles about ITA Software’s Lisp code and it’s really interesting.

Lisp may be a critical part of ITA’s success, but “good enough for Google” is probably the wrong take here—Google, I’m sure, purchased a company to add its working product to their portfolio. I doubt that Google’s processes would allow someone to ale a new product in Lisp.