CNN Erin Burnett OutFront May 6, 2015 23:49:00
It is rarely used but it is used in europe. there is a capability for air traffic control to read what you have selected not your altitude but what you have selected for altitude as well as your speed heading. it's called mode sierra enhanced. it is possible he was checking to see if this particular sector had that capability. the air traffic controller if he had seen it probably would have said excuse me where are you going right now, germanwings? and that might have been what was going on. >> wow. that's fascinating. even more sinister when you think about it that he was testing to see if th...
Source: archive.org