marcus, the scale of the devastation, so overwhelming. we heard the dire prediction from the u.n. official. what are searchers telling you about how many people may still be buried under that rubble? >> reporter: whit, usaid told us they have only been able to assess one-third of the buildings. as you know, a state of emergency has been declared in ten cities across turkey. it gives you a sense of how widespread the destruction is here and how many buildings they have left to fully assess. whit? >> marcus moore reporting all week for us on this. thank you. now, to that frightening collision at los angeles international airport overnight. four people sent to the hospital after what is described as a low-speed collision between an american airlines plane and a shuttle bus. the plane was being towed from a gate to the parking area when the incident occurred. this is the fourth accident or near-miss at one of the nation's airports in less than a month. here's abc's zarine shah.