How do I increase the volume of engine sounds of aircraft in Ultimate Traffic? If I turn the speakers to max volume I can hear the engines just fine but then the Palm Spotter volume announcements are way too loud.

YOu need to grab some AI aircraft sound replacement sets - there are some here and at flightsim.com

I assume that you are refering to the AI aircraft placed by Ultimate Traffic. This can not be set by the UT software but you can download alternative AI Aircraft sounds which are both lounder and more realistic sounding.I use aisnd.zip by Marcel Thomas, which is not available in the AVSIM file library. You can either Google it or go to Flightsim.com.

aisound_1.0.zip here in the library I've found is awesome. The only downside is to get the full effect of touchdown sounds you have to manually edit each aircraft.cfg for big small medium jets and props. It is great though and well worth it!