Not totally true. There was no priority for us last year coming back in from Costa Rica. Because of the time of day, multiple international flights were coming in, etc, it took us 2-3 hours to clear customs. Seemed that the non-citizen line was moving much faster.
When we got back from Argentina a few years ago it was a breeze, but we returned at 5am and beat the morning rush.
Just depends on the time of day and number of flights all coming in at the same time.
Next time we plan an international trip, I am going to apply for Global entry. Seems totally worth the $100 (or whatever it is) to walk right up and avoid the whole mess. I forgot about doing that last year and was kicking myself for it.
I'd have them call you when they land and get a look at the line. If it is short, head over, if they tell you it is wrapped up worse than the most popular ride at WDW, tell them to call you when they are getting close to the front. They will still need to get their luggage and go through another line.
They have to go through customs when coming back into the country. As people have mentioned above, some airports have US Customs agents there to check you before you board the flight back to the US. Everyone else has to go through customs when you land at DFW.
You really just need to figure out if they already went through customs in Amsterdam before boarding.
Nope that wouldn't be Saudi or Qatar. The pre clearance facility is built in Abu Dhabi - similar to what you see in Canada, Aruba and some other Caribbean islands. Right now there are no nonstop flights from Abu Dhabi to Dallas so this doesn't even apply at DFW - starting in Dec '2014 a non stop flight starts between DFW and Abu Dhabi