All of the above can helpful, but if you're really worried, call your physician's office and BEG for a scrip for A/B Otic, to be used only if really needed on the plane. It is Rx analgesic ear drops, and it will kill any ear pain within minutes. I know you don't technically have an ear infection, but blocked sinuses can create ear pain on planes, so a painkiller for your ears is a good emergency measure.
It can be difficult to get a scrip for this medication because it can mask the pain of a ruptured eardrum, and physicians do not want the risk of patients trying to self-treat that. I've got them, but I had to make a deal with my doctor, (and I made the same deal with my pediatrician, b/c there was no way I was going to let my kids suffer agonizing ear pain if I had a way to stop it). The deal is this: if I need to use the drops while flying, I will use them once on the plane and only once more afterward if it still hurts. If the pain is still there when the second dose wears off, I've promised to seek emergency medical treatment.
I'd also ask for an Rx nasal spray for the flight. Afrin works for many people, but it can create a nasty rebound effect after only a few uses. If you are going to go with a spray, the Rx steriod versions are much better. The one I normally use is Nasonex, but my ENT is generous with the samples he gets, so sometimes it varies.