It sounds trivial but it's not always that easy. I was on a flight from Narita to SeaTac that got a nice jetstream tailwind of around 200mph for most of the cruise. The same applied to another flight from Incheon to SeaTac.

Both of these flights were originally scheduled to land around 8am. They landed around 5am so they had 2 CBP officers on shift to handle a 767 and a 777's worth of people. That mess ate up the entire gain of arriving early.

They would have known about the early arrival not too much earlier than the departure time (order of hours, not days), which isn't really enough time to shift people's work schedules.

I agree that the logistics involved are not that simple. However, it _does_ appear to be a regular occurrence at SeaTac and there's not much that's different (went through that 3 times in 2 months and the experience was the same each time). Anyway, at risk of this going way OT, it was my colloquial evidence that not every airport is equipped to handle multiple concurrent international heavies.

Ever notice how only government services have hours long wait times: DMV, immigration, passport services, city hall, etc. Government has no incentive to optimize.

Many private services have long wait times too. It's not just a government thing.

...in the US.

> If only they knew when those flights were arriving so they could schedule customs and immigration staff to handle the traffic /s

Took me a few seconds to get this...:)