Personally I can barely tell or hear a difference between five/fife or three/tree....never really wasted enough grey matter trying to pick apart the verbiage while laneling the communicator as a tool.

As an FO, it's particularly annoying when you fly with a captain one week who gives you the old eye roll for saying fife/tree/niner, and then fly with another captain a week later who gives you the same old eye roll for not saying that way.


I imagine the guys who pinch a loaf with the way you say the numbers 3-5-9 in an ATC transmission probably have a problem with the way their first officers do everything else.