Perhaps 'trick' would be a better term in this airport case. I guess the difference between a trick and a hack is that you can't trick a machine (it does what it's told and doesn't care what your intentions are) but you can certainly trick people (they can be fooled in to misreading your intentions and responding dynamically). Also a trick is usually just about improving device utility rather than re-purposing it.
But clearly "hacking" can be used for things other than computer related stuff, and I feel like calling a clever trick "hacking" is less harmful (well, it's even harmless IMHO). Getting back to your comment, I feel that here it is a valid usage of the word. Take something similar for instance: calling Steal This Book [1] a kind of society hacking cookbook (it is mostly outdated though) feels completely right to me.
Defending the meaning of the word may be important, but wanting to restrain its usage all the time is useless and counterproductive.