I have had a similar situation... not flying though...
Went to Great America/ Six Flags Theme park... and i am a total freak when it comes to rollercoasters...

I have never had motion sickness a day in my life... when i was there i felt extremely sick on a few of the "old favorites".... so not sure if it is diet related... but since I have been there about 100 times on the same rides... and only since LC'ing has it happened... I would say it is connected..