I'm trying to get the 144 icon working for my retina app. I've seen many people say you can put it in the app by adding <image144x144>Icon_144.png</image144x144> to the icon section of the app descriptor XML. However, if I add that line, it just deletes that line during publish and doesn't publish the icon. I have my 144 icon with that name in a bunch of different folders in case it's checking a different one than I expect, but it never works.
I just looked in the descriptor template for the current AIR 3.3, and 144 is listed there. Maybe it wasn't listed before? It's certainly not in the AIR 3.2 version of that file.
Something else that seems new is that Flash made a folder named "AppIconsForPublish", and when I selected the 114 icon it put a copy there. There isn't an option for selecting 144, so I added the line to the xml, and also copied the 144 icon into that new folder.
Still it deleted the entry from the xml. Next I tried with 3.4, and still the icon was deleted from the xml.
So, it seems that because 144 isn't listed in the Flash publishing settings it gets deleted. It may be for now that you have to do the build from the command line, and that may work in 3.3 too.
I'll alert the authorities about how even AIR 3.4 deletes the 144 icon.