Without getting into the tired argument about computer resolution vs human eye, no icons could gauge a player's ability to recoginze and estimate some of the variables that make aerial combat both an artform and a skill. Using the icon makes it too easy to tell how far away you are, how fast you're closing, when the con is in optimum firing range, etc. Having never flown KOTH, I guess you're all in the same plane so plane identification is a non-factor in the "icon vs no-icon" discussion.
Isn't there already an icon mode (for friendlies) to show the plane type instead of the playerID?