I've used my BCT-15X for Mil and Commercial air for a couple of years now. Also use it monitoring railroads. Works fine on voice comms.
When attempting to use it for ACARS data from aircraft, my impression is that it does not have sufficient audio bandwidth for this. I have another scanner that works pretty well on ACARS, and there is a difference when you open up the squelch and hear the ambient noise. The BCT-15X does not seem to have the highs, and so I think it misses the synch signal that briefly appears at the start of these ACARS messages.
Also, I have noticed the BCT-15X is much more sensitive to my HF receiver's oscillators than my other two scanners. It will open squelch much more often, making it more difficult to use on the AM air bands, though this does depend on the specific HF freq to which I am listening.