I was contacted by Playboy Magazine (yes, that Playboy) because they had seen one of my soaring photos here on A.net. The single photo ended up used across two full pages with text inset. My FIRST Playboy spread.... alas.... she was a beauty..... my sailplane and I.
We negotiated by email, I sent the high-res scan by email, and they electronically deposited the funds into my bank account. Nary a piece of paper was used.
Other covers such as Flight International, Free Flight, Aerius have been through professional contacts via work.
The important thing is to think like a news photographer and illustrator. Once you get by the basic technical requirements (focus, composition, exposure etc.) you have to think of the news value to the publication. Pretty photos generally don't make it unless they have a news value or are directly related to, or used to illustrate a storyline. For magazine covers, you also have to think like an illustrator. Generally vertically framed photos, leave room for the headline, UPC barcode, and room for text headers that point to what is in the issue. Again, if the cover cannot convey the required information besides your photo, then your photo won't make it. But what a rush when it does.
Other ways to come to the attention of editors is to enter magazine photo contests such as the Aviation Week & Space Technology annual International Photo Contest. Slides ONLY (sorry digital guys) are the entry medium and you get great exposure especially if your image either wins or places well in one of the categories. And of course there is always the grand prize "Best of the Best" which is what we all strive for.
Hope this helps you with some ideas and direction.