Some words may not be present in the dictionary built into the Microsoft speech recognition system, which makes recognition less accurate as there is no pronunciation reference for that specific word.
You can add words to the dictionary and record your own pronunciation for them:
Click the wrench icon on VoiceAttack's main window, and on the "Recognition" tab of the VoiceAttack options window click the "Utilities >" button, then choose "Add/Remove Dictionary Words"
If you're using the US English speech recognition engine, "Airborne" is a standard dictionary word, with that specific spelling.