FWIW I took our son to see the Doctor 2 days before we were due to fly as he had been off colour over a weekend. He was then diagnosed with a bad ear infection. That Doctor advised us strongly not to fly and to delay our flight out by at least 3-4 days. As this would have landed us slap bang in the middle of the BA strikes and no hope of getting on a plane then I took the executive decision of putting him on the antibiotics straight away and going back 24 hours later for another check up. This time I saw another Doctor (a lady and a parent) and she said the bad ear was looking better, the good one, worse However, she did say if it was her travelling out she'd chance it and fly. A woman with my way of thinking.
We'd heard the worse case scenarios (ear drum perforating or a pained screaming child the entire flight) and hubby and I talked it over and decided to fly anyways. If it had been to Spain we'd have delayed, but out to Australia, it wasn't so easy to do that. He would have had 48 hours of antibiotics in his system by the time we took off and they work really quickly in kids. We kept him on Calpol/Nurofen every 4 hours for the flight also. And earplugs. He was fine. Slept loads as we flew overnight, didn't scream, cry or fuss at all. Was amazing all things considered. In fact, easiest flight I've ever had with a kid :v_SPIN:
Hope your little one perks up by the morning :)