A lot of things in Aviation are learned the hard way from the experiences and mistakes of others. It is terrible to think that it took the loss of 137 lives 26 years ago to start the development of TCAS, however I am sure that over the years it has saved 100 maybe even 1000 times that many.Tcas is a great safety system which has saved my own Bacon on adeparture out of PHC (Port Harcourt Nigeria) a few years ago when ATC cleared a 767 to land as we were on climbout in a A300 meeting each other. All ended well but ther were a few skid marks on the cockpit seats that day I can tell you! Another shining example of ATC in Africa