A visit to LAS
to any given day can turn into a military air event!. KC
-135's, C-130's, F/FA-18's F-16's, etc., etc. are common visitors nearly everyday. In fact, it is not uncommon to be landing at LAS
in a Southwest 737 and you are following 2 F-18's in formation. During Red Flag, which is now going on, it tends to elevate. You will also see many RAF transports (VC-10's & L15's) along with Eurofighters, Tornados, etc....
From what I understand, the primary reason is the fuel contract. While most Nellis based equipment is fueled at Nellis, contract fuel (that gets you the best rate) for everyone else including the USAF
and RAF is through Signature flight support, so many a/c transitting in and out of Nellis tend to fuel at LAS