Is there a benefit to multiple interceptors on one satellite?
Solution 1:
I've seen two benefits:
Possible to continue a failed attack on a UFO. If the first interceptor dies or aborts you can launch a second interceptor - unlike David Burton I haven't had any problems doing this.
Possible to equip different weapons for different targets, such as high power weapons for larger UFOs. I'm uncertain if this alters what can be recovered on the ground (ie overkill = less items), but I wouldn't be surprised if it does.
Solution 2:
I have found no bonus to dispatching two, but a fatal bug.
I recently dispatched a second interceptor on an airborne UFO by clicking on the UFO graphic and selecting my second interceptor. Do Not Do This. I downed the UFO with first craft, then Skyranger came in and soldiers cleared crash site. On mission complete, that second interceptor did not return to hangar, but drifted to north pole lol and the game went to the geoscape display, but in a zoomed in fashion. I could not esc out or do anything to exit this problem. Closing program with task manager does work.