To any magazine, flying or otherwise:
Always send a SAE, asking for return of your material. Then if you don't hear anything, you can phone and ask if they're thinking about it, or planning to send it back.
Sometimes they're busy, or confused, or plain incompetent. It doesn't necessarily mean they don't want your article. I phoned several months after sending my last one to Pilot; the editor wanted it, and thought he'd told me, and thought I'd been paid. I hadn't heard a thing. Eventually, after another phone call, I got paid, and the article was eventually published nearly a year after I sent it.
I've had automatic acknowledgements, and then never heard anything ever again. One thing you can do is send a stamped postcard with the rest of the material saying: Article and photos received safely on .... That way at least you know they got it.
I've had efficient and inefficient responses/dealings with both the main flying mags, and other mags too. It seems to depend on what else is going on, how busy they are, all sorts of things. But they do get a lot of stuff sent on spec, so unfortunately your precious article is only that important to you. Unless you've been commissioned or done something really unique, I suppose - I wouldn't know about that.