Well, I think in this special case we have to surmount the air resistance outside the train. That means that the train would go on while your 'flight'. The air resistance provides you the ability on the top of the waggons for a better backward going as for a forward going.

But nevertheless it is Einstein's theory of relativity. Just in this moment when you're jumping up to the air you'll leave the relationship to the train for a moment...

But inside the train the air is a part of the train. That means that the air is related to the train - a closed system.

[This message has been edited by Sheriff (edited 05-11-2005).]