ITA actually has two large Lisp systems. One of them is the insanely optimized fare search system (QPX) that does all the crazy things described in the link. Th

ITA actually has two large Lisp systems. One of them is the insanely optimized fare search system (QPX) that does all the crazy things described in the link. The other is the airline reservation system which is a much more conventionally coded Lisp system.