As an amateur holster-maker and firearms enthusiast, if I were going to put a padlock on a holster (and I wouldn't BTW), I'd put it up on the thumbbreak/retention strap. Putting the lock through the triggerguard is unnecessary and evidently dangerous. Let the leatherwork protect the trigger like the Good Lord and John Moses Browning intended.
I see no reason why a pilot who has put himself through the requires red tape and training can't keep a hot gun in the cockpit. Israeli-style draw may work for the IDF, but a round in the pipe is a good thing to have when you really, really need it.
Better idea - lockbox.
They had a box, of sorts. But only those pilots who are FFDO's could have them, and they had to be carried off the airplane, making it obvious, to the casual terrorist observer which planes had armed pilots and which did not. It was pretty heavy to be lugging around the airport along with the regular bags, chart case, etc.