"I wonder why they did not divert to RDU
How did GSO
do the immigration and customs?"
has a customs office for various cargo carriers and are capable of handling customs for any passenger carrier. This is listed in the airport data for the Southeast put out by the FAA.
As for why they didn't divert to RDU
. If my memory serves me, typically when there is an emergency situation, airspace is cleared for the aircraft in question. Depending on the issue, they may have wanted to put the jet in question into an airport that had the minimal amount of service they required (ie customs, long field, etc) but also with the least amount of traffic possible.
was probably one of the only choices. It also depends on where the craft was when the problem was reported. If it was over eastern NC
, perhaps Norfolk or Richmond would have worked, once you move farther out, then maybe GSP