[DanBC]

Yes, now that a plane has disappeared (instead of just being flown to a different airport and hostages kept; or being flown into a building) means that there is a reason to implement costly tracking devices that previously had little use.

I used to build devices for aerospace. These were groundside, never ever airside. The systems (and thus costs) for building these devices were extensive and complex. Every item, every component, every screw, every washer, all the chemicals (paint, conformal coating, etc) could be traced from a finished unit (via its serial number) back through the manufacturing chain. When my company moved from a paperworks systems (suprisingly good) to computers (unsurprisingly flawed) they kept the paperwork system for these products because it was so important to never fail audit.

It's easy to look at consumer grade off the shelf systems and think that the cost would be maybe four or five times higher, but I think the cost would be significantly greater.

Add to that the difficulty of getting any component on a circuit diagram changed and the need to continue producing these units for every aircraft for many years and there's additional complication there.