This is not exactly what you are looking for, but I recently discovered Lucy Activewear. I had an hour to kill while waiting for an Amtrak train in Union Station (DC), and discovered this store. They are allegedly more for "working out" but I got 2 pairs of pants. This pair works great as being supercomfy and looks nice, perfect for long flights:
http://www.lucy.com/jump.jsp?itemID=...th=1%2C2%2C235
You can even dress them up. One hint is that they have zippers on the outside of the legs that you should zip up by an inch. They are not noticeable but if you don't pull them off, they clink on the floor.
They will be the pants I wear (with my Merrell's) on all my flights for my upcoming whirlwind business trip to Asia Pacific.