go through directly a thunderstorm. >> it's our understanding that the pilot -- the captain asked for a deviation in the flight route, asked to go higher. how stable is the plane at those altitudes, some 36,000 to 38,000 feet? >> well that's a great part of the question. but before i get to that answer and i'll get to it very quickly. let's not jump ahead of ourselves. the request for higher altitude may have been because they were experiencing choppy ride. it may not have been unbearable. we all want to make our ride comfortable for passengers. as far as going to a higher altitude my understanding of the a-320, about a 49,000 max service altitude. when you get up to the thin air, called coffin corner where the performance of the airplane is such that you are close to the max airspeed that the airplane can attain and very close to the lowest airspeed you can maintain