The issue of stuck transmit keys can be mitigated by the fitting of "Contran" which automatically deselects the transmitter after (I think) 30 secs.
This system also prevents crossed transmissions by inhibiting your ability to transmit should you begin to key the transmit button and another station is transmitting.
I believe Britannia have this system fitted to most of their fleet and it is arguably true that if the aircraft at Tenerife had been fitted with such a system the worlds worst air disaster might not have happened.