I second the post above that the issue of a deep vein thrombosis (DVT) has been overblown by the media. The classic case of DVT we learn in med school is someone who has taken a long car trip, where presumably one has more leg room than in an airplane. The key in developing a DVT is sitting for long periods of time, not so much the amount of leg room. My advice is to avoid a DVT, make sure you get up and walk down the aisle at least once or twice during a flight.