If you are developing using Air 2.6 you are probably using the menu softkey to make users navigating the application.
When you will upgrade to Flash Builder 4.6 the menu key will disappear!
In effect, as the bug report 2936827 reported against Air 2.7 explains, Air 2.7 is targeting, by default, Android SDK 11. This makes your menu key disappearing.
I think you, and our, must try to not use the menu softkey but, in the mean time, you can re-enable the menu soft key setting up the
targetSdkVersion in your AIR application descriptor:
<android> <manifestAdditions><![CDATA[ <manifest android:installLocation="auto"> <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="10"/> [....] </manifest> [....] ]]> </manifestAdditions> </android>