Transiting Procedures Through the US with Firearms
After much discussion and many phone calls, most leading in circles, I have determined the regulations for the transiting procedures through the US via air with firearms.
No permit is required to transit the US via air with firearms provided the firearms do not pass through US customs while in the US. Have your export, import permits, proof of ownership and either a hunting lisence or other supporting documentation (Invitation to hunt/shooting event) handy at the time of passing through US customs in the country of departure.
If you have problems with a flight resulting in an extended layover while in the US, under no circumstances claim a firearm or baggage containing ammunition in the US, intruct your airline to keep your baggage until a suitable replacement flight is available. If your firearm pops out on the baggage carousel or your airline wants you to collect it from baggage claims, DO NOT TOUCH IT, instead have someone watch that the firearm does not get stolen and immediately report the occurence to US Cuctoms and Border Security, a smiling agent will happily get the firearm back where it belongs. DO NOT try to take your fire arm to US Cuctoms and Border Security, allow them to collect it themselves. Under no circumstances take any chance of being in posession of a firearm in the US without proper import documents.
SAA has policies in place and will not return firearms or ammunition to passengers in the US, United does not and requires that the passenger request that United hold thier luggage until a replacement flight can be arranged. I do not know the policies of other airlines, check before you fly.
Dept of State DSP-61 permits are a form of temporary import permit, not an in-transit permit. They are for military items entering the US temporarily, for trade fairs and such, that are not covered by the BATF regulations for sporting arms and are only reguired for items that will be clearing customs on US soil (officially entering the US).
I hope this clears things up in this very gray area of US law.