I am glad you are going to find out what you need to do to stay safe. I read that between 60-100K Americans are estimated to die every year from DVT, so it is a serious concern, particularly when flights are over 3 1/2-4 hours. I have also heard not to sleep, and since we have a long international flight coming up, I told my husband I was going to slap him in the face every 30 minutes, to wake him up and get his heart rate to increase. Maybe your H would be willing to do that for you? 