Originally Posted by
ESpen36
I suspect (strictly my suspicion) that the true "direct" one-stop flight, without deplaning, happens more often overseas, where no immigration/customs checks occur for transiting passengers. The WN example makes sense because it uses a point-to-point model, so there wouldn't necessarily be additional aircraft at many stations for swapping equipment on direct flights.
Unfortunately, your theory is not totally correct. While there are no customs and immigration checks in most of the overseas countries, nearly all Asian countries do require deplaning and re-screening through security, even if you're getting right back on the same plane. I can speak to personal experience on this on transits through NRT, HKG, and ICN at a minimum. The BKK CX example above is one counter-example to this. But even the RJ flight HKG-BKK-AMM requires deplaning (though no security re-screening).
So it may happen more often overseas (since on international flights it won't happen AT ALL in the US)...but it still isn't the most common practice.