Hi there
During my last flight Im sitting at the rear carbinet of 777-300Er. I see silver / white something going very fast from the rear of the engine to the last row’s window.
This going fast thing also is very obvious if there re sunshine.
What is this? Flowing air? Possible fuel leak?
Yes, it’s normal. 
For further research please see the following: http://en.wikipedia.org/wiki/Contrail
