Are you civilian aviation or military aviation?
There is a civilian aviation receiver on Amazon I've seen a number of times and it some of the ham radio shops across the country. Would the civilian aviation frequencies, you would want to be monitoring normally between 118 - 136.975 MHz.
If it's military that you're talking about, the receiver would want to receive between 225-399.975 MHz for the most part. I don't think there is any specific military aviation only receiver. I could be wrong but if there had been one I would have bought it by now myself
What you probably want to get is a scanner that will pick up both of those bands. And even though the one at this link I'm posting is a great, cheap receiver, don't buy it at this Amazon price. It's gone up $35 since I was looking at it less than a week ago. It's normally going to cost you about $120 - $130 but they put it on sale every so often for about $89 at many of the vendors. And you can find it cheaper shopping around that some of the ham radio stores online. It's the unit in BC125AT scanner, it's small and easy to carry, and it will pick up the frequencies for both of those bands.
Again, the price at that link is ridiculous. But if you take that model and do a search for it you will probably find it from other dealers at a much cheaper price. It's definitely not on sale right now so you would likely spend at least $120. But it is great for aviation monitoring and a lot of people use it solely for that. It will allow you to program 500 frequencies/ channels in also and you can name the channels as well. They call that alpha tagging which is the AT at the end of the model number.
Brian
COMMSCAN