I'll have to dig out my camera . . . .
In the meantime, I did a side-by-side comparison:
While the cap on the Recife is a bit longer than that on the Airmail, the two pens are exactly the same length capped and uncapped. The caps are, in fact, interchangeable; however, the Recife cap has a few more threads and thus the body seats a little deeper.
The clips and cap bands are nearly identical except that those on the Airmail are blank. The band on the Recife has the brand name and the clip on my Recife says "Disney" (this is a special edition made for Disney; I can't put my hands on my other Recife right now to check the clip on that one).
The sections are very similar, with that on the Airmail perhaps slightly thicker; but the difference is negligible if it exists at all.
The barrel of the Recife appears to be a bit larger around than that of the Airmail. It's unclear whether the Recife accordingly has a somewhat greater ink capacity or if the plastic surrounding the ink reservoir is thicker.
The Airmail barrel is imprinted "Wality"; that of the Recife says "Recife."
The biggest differences are between the cap crowns and, of course, the nibs and feeds.
In sum, the Airmail is nearly an exact clone of the Recife Crystal. (I'm assuming that the Recife predates the Airmail--I don't know when the Airmail first appeared, but I bought one of my Recifes back in the late 1970s.) In any case, if you're thinking of getting Airmail instead of the more expensive Recife, I'd say go for it. Hope this helps.
If it isn't an imposition, I'd be interested in seeing a picture of them side by side, both the pen bodies with section, and the two caps.
I've never been comfortable pulling a feed out of a section.