questions about the co-pilot's cell phone. officials say it was turned on and searching for service around the time the plane van earned from radar. you have been tweeting us your questions by the thousands, and we have top aviation and security experts standing by to answer them, like this one from raymond. with all this technology we have, why did they wait to deploy a blue fin sub, why now, 38 days later? now i want to go right to cnn's reporters in the search zone. joe johns is in kuala lumpur. on this first day of being deployed, bluefin-21 had to l n return to the surface many hours before planned. what can you tell us about that? >> reporter: it speaks to what we don't know about the ocean floor there. as we've said before, we know