Saw it once in the DC FRZ. I was cleared to enter the Gruby gate when I noticed a 172 about a mile off entering on a parallel course. I called out to him on the correct frequency and didn’t get a reply. I jumped over to fingers, tried again, and still nothing. At that point I could feel the F-16’s taking off from Andrews. I just moved over a bit to get some separation and sure enough in under a minute Potomac informed me that interceptors were arriving in the area and to keep my course and speed as required to get to KVKX. As for the 172…free air show!