Originally Posted by
idiparker
FWIW we had the secondary check for a US-bound flight, eventhough we stopped first in Narita (and nearly everyone got off). So if you are on a US-bound flight, or a short hop that continues on to the USA, expect the carry on check.
... or ANY flight operated by a US carrier that originates at a non-US airport, regardless of destination. The flight doesn't need to be continuing on to the US in order to get the special treatment.