Wirelessly posted (BlackBerry9000/5.0.0.822 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/102)

I have, but not in a while. It was more common when multi-stop flights were more common and you exited the aircraft at the stopover airport.

On Swissair. Flying BOM-HKG, they checked boarding passes at HKG to ensure only those disembarking in HKG got off the plane first, since the flight continued to Seoul.

On Zambia Airways, they used to check your BP on exiting the plane and give you a green laminated card to hold on to if you were continuing to the next stop.

Most countries now have a document check at first point of entry rule, so that eliminates the need to check BPs and segregate people. But we still have the outdated "international connector" concept so there's no escape. Australia is the one other country I know of where domestic and international passengers were mixed on the local leg of the flight.