Flight times mystery

My frequent trips from Dallas to California resulted in an interesting observation.
90% of trips from Dallas to CA took around 2.5 hrs.. But the return trip took around 3 hrs.. Everytime I observed this, I would make a naive assumption that this was coz of the earth's rotation and put it off..I didnt really ponder over the real reason.

Incidently on my most recent trip, the statistics were reverse. Dallas to San Jose took 3.5 hours and return trip took just 3 hours.. Again, the naive assumption didnt work.. This made me go back and see why I was dumb earlier.

I am going to use my OOP concepts and implement reusability here.. Since someone has already put an explanation, follow this link...
'Earths rotation and Flight times'

And being in the S/w industry for so long, I also understand reliability of systems is not guaranteed and hence I have a backup link for same explanation..
Newton explains

Reading online articles for so long has also made me believe related articles are important.. So, if anyone still believes that Bermuda Triangle is still a mystery, you got to read this too..
'Bermuda Triangle explained'

By the way, I knew Bermuda triangle mystery was untrue long before it was even formulated.. :P