To the OP, Check out this link for more information about using your car seats on an airplane. Pay special attention to the part towards the bottom that explains about flipping the buckle on the airplane's seat belt so it makes it easier to release when you are getting off the plane!
If you have any questions, just give me a yell. I'm a Certified Child Passenger Safety Technician and even though 99% of our training is for usage in cars, I have some resources for airline use as well.
Good Luck!
Since you are a certified tech, I will take the opportunity to ask: any thoughts on the new FAA certified harness? I am considering purchase for DGD.