CNN At This Hour With Berman and Michaela April 10, 2014 15:08:00
Escape the busy commercial traffic lanes up above 18,000 feet. without a transponder, you would be at risk for a collision avoidance problem because your collision avoidance equipment wouldn't work. you'd need the transponder for that. so there are lots of reasons to go down. the issue is, you know, this is suspect information because they have it on radar, and then they don't have it on radar. this is a boeing 777. this is not -- you know, this is not a jet copter. it doesn't go from 35,000 feet to 5,000 feet in the blink of an eye. so didn't radar pick up the ascent and the descent? somethin...
Source: archive.org