Bing has just rolled out interior maps of many U.S. airports. Specifically, you can now browse detailed and accurate maps of the concourses of 42 different airports. To do that, just search for the airport in question and then zoom in. If the airport is supported, you'll see where every airline check-in counter, Cinnabon, ATM, and rest room are located.
I found that Bing has maps for Newark, JFK, Sea-Tac, LAX, and others. It's clearly not a complete set of large U.S. airports -- I discovered that Chicago is notably not yet represented, and the maps are currently on the PC, not phones -- but it's a great start and a handy resource.
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