How to write an intinerary email that Gmail will recognize
What I've done in the past (you're not alone in this want!) is take other emails that I've gotten from other flights and replaced all the information with my new flight that I wish to track. Make sure you hit the most important parts


Itinerary number
Confirmation code
Flight numbers
Incoming/outgoing airports
All flight times


Once I filled in all my new information, I just forwarded myself that email and Gmail picked it up and even pushed the info into Google Now!

Pretty handy.