Or simply omit, since it is a very light foam. I would include it though, despite the fact that the term sounds a tiny bit awkward, as can been seen from this reference, in which they keep qualifying the air as foam in brackets. I would use "airs". I will post some more references shortly.

http://moleculargastronomy.wordpress.com/2010/01/03/emulsion...

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Note added at 6 mins (2010-08-25 13:50:30 GMT)
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OK definitely use "airs".

"You’ll be making airs, foams, spheres and edible pearls before you can say ‘Ferran Adria’."

http://justcookit.blogspot.com/2009/12/molecular-gastronomy-...

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Note added at 8 mins (2010-08-25 13:52:01 GMT)
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"This is our complete Molecular Range of products and contains everything you need for the production of spheres, ravioli, foams, airs, oil based powders, noodles, gels and the emulsion and thinking of liquids."

http://redspooncompany.com/store/index.php?main_page=product...

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Note added at 25 mins (2010-08-25 14:08:44 GMT)
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"Downstairs, in the restaurant proper, we found a large table, beautifully dressed. The lunch set menu is unfathomably well-priced at £19.95 for two courses or £23.95 for three. I chose from the a la carte menu, largely because I had been fantasising about the restaurant’s signature white onion risotto with parmesan air and espresso ever since booking."

http://www.gastronomydomine.com/?p=338