there would be all kinds of noise in the cockpit, in the cabin. go ahead, miles. you want to present that to martin? >> yeah. there are two things to consider. they had just had the handoff. in other words, the frequency change. they were told to go on to 120.9. and so what a pilot does when they say good night, at that same moment you flip the radios. if nothing else so you don't forget the frequency. and it stands to reason that two things happen. first of all, they probably didn't have time to make contact with ho chi minh. they might have been in a dead spot. a lot of times you make those frequency changes, it takes a little while to raise the controller. so then in that scenario if something bad happened, the thing to do would be to go to the previous frequency, kuala lumpur. but that's one more thing to think about when you've got all kinds of bad things happening at once. so it just adds one more thing to the mix and helps explain why maybe they didn't get the radio call. maybe they were trying to call on the ho chi minh city