I can't speak to all of the 210 +/- folks that have left my company in the past 14 or 15 months; or since I've been here for that matter. I was hired in '15 with a Guard C-17 driver who did two rotations and went to Delta. I have another good buddy who got a call from American after three rotations.
Calls have come from SkyWest, Frontier, Atlas, Omni, FedEx, FlexJet, United, Delta, American, LEIDOS, VistaJet, WheelsUp... It all depends on the individual as to what they target and when. (We also have Regional FO's coming to us for PIC hours and better pay vice waiting in the Minor leagues for the call-up once they get a number of 121 Jet hours in their logbook).
I understand the benefit of 121 Jet time and the economics of getting hired at the Majors as soon as possible.
However, for someone non-current, to get quick hours and good pay, or to get FWME time in their log book vice Viper, Reaper, RW, or Osprey time, this isn't a bad spot. I'm not implying that ISR is the best way to get to the Big 6, but a PIC can earn about $52k for two months of work and 160 to 250 flight hours. They then have two months off to do what ever they want, including leaving for a regional or preparing themselves for an interview at a Major. If it doesn't work out right away for someone with a strong military background and jet experience elsewhere, earing $155k per year with good benefits and 6 months off per year until it does isn't terrible.
I may be a bit biased towards this job, I came here to do about a year and have stayed past three... by choice, having never submitted a resume or application to anyone since the summer of '15.