You are assuming that the glidepath is the only reference for an aircraft on a CAT III approach. But CAT III (and II) also require a radar altimeter, which would foil a Die Hard II scheme.

  In addition, the aircraft would not be at the proper height for its location along the approach.

But it was a fun movie to watch, even if extremely unrealistic.

tlhIngan wrote

In North America, there is ONE refinery still producing it. And they pretty much only run a batch once a year - an entire day's production is sufficient for an entire year. Something like all the avgas used in a year is equal to all the regular gas used by cars in a day.

Don't suppose you have a reference for that assertion do you? There are several refineries in USA that make avgas, and production is much larger than a day.

In 2009 there were 10 refineries making avgas, this article indicates there "seven or eight" in 2011.

Check out this table , courtesy of the Energy Information Administration, for a summary of regions where avgas is produced.

Engine kill anti theft devices based on keys with chips on them have been in place for years. Cars equipped with them at the factory still show up in the Top Stolen Car lists. It's a nice idea, but certainly not fail-proof and devices like aftermarket alarms bypass the anti-theft systems before the thief even arrives.