Hi there,
Check this out-
http://flightaware.com/live/flight/BAW242
This one confused me just a little. Did BA start new CHA-LHR service? 
Ideas?
Regards
JetBlast @ BWI
Look at the flight status. At 1:44 a.m. (“departure” time from KCHA), the a/c is at 33000ft. I think they filed a flight plan while in flight from MMMX. I didn’t know that could be done (I’m not a pilot), but it definitely appears that they DID NOT take off in Chattanooga. Also, look at the green tracking line that starts west of KCHA and continues eastward through it, rather than starting there.
It was a new clearance from ATC, possibly due to a change to the North Atlantic Tracks or to avoid weather in the US.