Interesting explanation in the 'pedia for why it's one of his few books not to become a movie
Crichton stated this was due to the great expense needed to make such a film. Another consideration might be that the novel is so dense with technical references that it reads more like an accident investigation report than a suspense-filled page-turner for the general reader. Airframe is unlike many of Crichton's other works in that the story has almost no outright science fiction elements.
I don't see why it should be particularly expensive to make. The few scenes that require flight can easily be handled with CG, and the rest takes place mostly in offices.
The technical references aren't an issue either. Harry Potter books that range from 312 to 872 pages have been adapted, with the bulk of the magic detail obviously dropped.
I suspect it's the lack of sci-fi elements they mentioned, plus a bit of a funding problem, as the major studios most likely share corporate parentage at some level with aerospace companies.
