I flew with Allegra from Sydney to Dubai (non stop) and from Dubai to Zurich when she was just shy of 6 months and she was fine. People are mainly supportive and offer you a break if you want a few minutes to yourself!
We were really lucky as she cried all up about 2 minutes on the way there and about 4 minutes on the way home and we were travelling for about 30 hours on the way home because we had a 8 hour stopover (we did have a hotel room though so we were able to rest)
Domestic flights should be a piece of cake! Take heaps of clean muslins and things so bubs can lie down etc and bottle or dummy etc for ear poppping as has been mentioned. The other thing that I found useful was toys for her to play with and by baby bjorn as it was so handy in the airport so I had free hands and also when we arrived in Dubai they had no idea about baby seats (let alone rear facing ones!) and so I was able to have her strapped to me and me belted into the car.