OP isn't asking for many-to-many; he said 1 destination airport from any origin, which is still one-to-many, or many-to-one inversely, so the difficulty isn't due to exponential edges complexity.

The real reason why it's harder is because airplane routes are a digraph. It's much easier to traverse in search of child nodes than it is to be given a child node and asked for its parent. Short of using DP, you'd have to traverse the ancestor-descendant path twice per ancestor node. If you were to visualize it, it'd look like the mythical world tree with countless roots turning each tip into yet another mirrored world tree until it refinds the starting descendant.

Easy example for other laymen:
A____B___C
^\\v ^||v v//^
_____D

• If I start from B as the origin, and I want to find all the possible destinations, I traverse to D, then from D to A & C. This is enough to prove that A, D, and C are destinations from B.
• If I start from B as the destination, and I want to find all the possible origins, I go to D. I can confirm D is an origin because I take the directed path back to B, which proves this is an origin-destination relationship of D->B. I now go from D to A. To prove that A is an origin (A->B), I must traverse, WLOG, from A back to D back to B. The same goes for C.

I have been wanting such a tool for ages.
I like the Google functionality of saying you want to start in NYC and go to "Europe"
The reverse would be very helpful for me, indeed.

Again - Kiwi allows you to search from e.g. Europe to JFK in business. It is not perfect but gives direction. You can book elsewhere.

ITA also had multi-country functionality years ago but no longer.

Used to love this feature of Matrix. It was very powerful Shame it got taken away.

Now if any of you were naïve enough to ask chatGPT for any such booking tricks, I am sure you were told that it is just a language AI and not an airfare database...:p

Adding another vote that this would be very useful…

I use ITA matrix (note you have to do this on a per-country basis, meaning when searching from A to B, where B is what you want, all airports in A have to be in the same country as A).

So say I'm trying to find flights to my hometown airport of DTW. What I usually do is pick an airport centrally located (or depending on what you're doing, you can use a more localized airport) and select the "nearby airports item" and change the filter to 2,000 miles. I then select all the airports I want.

It's not the best, but it does work.

can I just say that kiwi is lifechanging?! had no idea this existed - thank you for sharing!!

That was a huge loss.
Would love to see it make a comeback.