Blood clot questions

Just getting on a plane you are at risk for a DVT.  Athletes are at increased risk as are smokers and women on birth control pills.  Wearing compressive gear on the plane will decrease your risk and also if you can get up and walk a little every hour.  Also (since I know your history) I know you had knee surgery with in the last 6 months or so (?) so that may have predisposed you as well.

Not sure what the US tech saw, probably that you had decent muscle mass and you are not all fatty   He probably saw teh DVT and maybe some swelling as to the "gee your calf must be sore " comment.

For your upcoming conference you  certainly won't do yourself any harm but wearing some compression hose but the risk sitting at ground level vs a flight is much much less. 

Some recent info on athletes and blood clots, and prevention

http://www.theglobeandmail.com/life/health-and-fitness/health/athletes-at-elevated-risk-of-blood-clots/article19378004/?cmpid=rss1

I remember reading somewhere that people with lower heart rates and blood pressure (typical of endurance athletes) have a greater tendency for blood to pool in their extremities.

I used to fly a lot on business overseas.  I'd always get up and walk a few laps around the plane every couple of hours during the flight.  I'd also do some isometric contractions of my leg muscles while seated.

Mark