by 1989 all aircraft operating up to 10,000 feet within 30 miles of terminal control areas must be equipped with transponders that convey altitude information. by 1993 all commercial carrier aircraft with ten seats or more operating within u.s. airspace are equipped with traffic alert and collision avoidance systems, tcas. >> the culmination beginning back with piedmont flight 22 going through the psa accident and then finally through the cerritos accident were all building blocks to promote this technology, which evolved into the modern system of tcas, which is a great predictive tool. >> the faa really had to take the bull by the horn, if you will, and do something to try and prevent these accidents from occurring. we increased or enhanced radar coverage.