I would like to add some information on international flights landing in Las Vegas between midnight and noon today. Here they are:
from Toronto US160 1007, AC591 1057
from Calgary AC546 1048, WS(Westjet)354 1144
from Vancouver US395 1035
from Mexico City MX990 after 0911
from Guadalajara OAE107 0051, MX996 1010
from Montreal AC575 1125
I happen to agree with Chateau's analysis that says you back up from an approximately noon sighting and then subtract an allowance for getting through customs/immigration and getting from McCarran (5 miles from the Las Vegas central Business district). I am using 1 hour total, so that means flights must land before 11am. That means that the prime suspects are US160 from Toronto, AC546 from Calgary, US395 from Vancouver, MX990 from Mexico City and MX996 from Guadalajara.
The next step is to work backward from the departures in the above cities to see the window for incoming flights from Europe to there.
Those departures are:
Working backward, here is what is possible in the right time frame incoming from Europe on this morning:
into Toronto - AC84 from Tel Aviv landed 0540; that's it because the London flying into Toronto is London Ontario
into Calgary - nothing, with incoming from LHR late afternoon and evening, too late to be useful
into Vancouver - nothing; although there are later arrivals from Amsterdam, Dusseldorf, Frankfurt, London Gatwick, London Heathrow and Charles de Gaulle, none is in the right time frame
into Mexico City from Madrid IB6401 arrived 616am
into Guadalajara - nothing except for cargo flights in from CDG and FRA
So the theory I am using is not working too well with nothing except one flight from Tel Aviv and one from Madrid this morning in the right time frame. Those are not the right cities for European deaprture points. I am returning to my prior theory of flying Prague to Atlanta, then connecting Atlanta to Las Vegas.