135.9 unless things have changed greatly since my glory days with AsA (choke, choke) the restrictions placed on fam trips are instigated by AsA itself and not by the airlines.
For as long as I can remember DCA, CAD, DOT, CAA, AA or whatever they have called themselves over the years, they have been the ones to place as many obstacles as possible in the way of ATC's getting famil rides.
Whenever I go flying, which is quite often these days , I always make an effort to visit the cockpit early in the flight (so that I can get stuck into the free booze afterwards) and I can say that it is never a wasted effort. Occasionally the crew can be less than warm, but so can we all, and I always learn something that is usefull in the job.