First, congrats for the decision to buy your own headset! It is a nice thing to have and reliefs one from feeling strange on all the hygienic may-be's ...
As flying is not cheap anyways and we talk about your hearing aids -> go for the most expensive one you can afford! Save on other things and focus on one. Once you have done damage to your ears, almost no money of the world brings back what you lost. My advice, go get an ANR one. Their protection is quite remarkably better. Only if you are really and absolutely short on money, but with a perspective for earning more, you could get a passive one and use it for passengers later on.