And to think Einstein spent all that time and effort proving that all time was relative!
More to the point time, according to general relativity, is dependent on the gravitational field, so those of you flying at 33,000 feet experience a different rate of time as observed by those people on the ground whether they be in Greenwich or France.
Does anyone remember that in the 70s they conducted an experiment with two atomic clocks? They were synchorised and one was kept on the ground while the other was put on a supersonnic jet (Blackbird?) and flown round the world. When it landed the the two clocks were out of synch.
Now I can't remember whether the clock in the plane gained or lost time but I don't think it is much to worry about even if you do spend large amounts of your 'time' in the air.
------------------
JJC