@coolwarriorisl....GOD you are abusive, arrogant and quite a show off...People call such th e problem child..dude should've read the terms and conditions...good 4 you...your story is quite a crap...makes no sense....
As far as your question is concerned...i would like to add that there is a continuous increase in height level from LHR-ISB...and CNG doesn't provide enough power to engine to accelerate...while things get different on petrol...
I have witnessed this in my car when climbing came right after salt range and i was literally flooring my car but it was not accelerating...though i was on petrol...