I don't think your Realtor had to "disclose" that you were under a flight path. The airport wasn't hidden. Same as if your home backed up to a major Interstate. Or a house directly under high-power lines. It's there; you can see that it's there; and you make your choice.
As for the appraiser: The appraiser used comps--comparable properties--to determine the value of your home. In all likelihood, comparable properties are ones close by, also underneath the flight path. So while the value of your property might be affected by the flight path, so are the values of the comparables. It would have been relevant to mention and adjust the price accordingly if yours were under the flight path but the comparables weren't.
Having said that, I understand your situation and your concern. And, yes, it may make your home more difficult to sell. But while the flight path may lower your resale value, it also meant that you were able to buy the home for less than you'd have spent for a similar home a few miles away.
There are ways to reduce the sound somewhat.
And you probably will get used to the sound. Quick story: My wife grew up in a medium-sized town, with her home maybe 1/4 mile from the airport. There weren't big jets, but there were a lot of smaller planes flying in and out--vacationers, business, etc. The first night I was at the house, it sounded as if we were right at the end of the runway. And we almost were. I commented on it, and she said she didn't even notice the sound.
Interestingly, her brother and sister-in-law recently bought a nice home in the same state, different town. We were going up to visit them, and I pulled the location up on MapQuest. Their nice home--on a lake on one side--was literally at the end of a runway. There was the house, maybe a 25 yard driveway, a two lane road, and the end of the runway right across the road. Now, the airport wasn't as busy as the house my wife and her brother had grown up in, but still . . . They didn't notice the planes at all.
Hope that helps.