Heard from a few sources of an Australian pilot who had just been given a job with Virgin Blue was heading over to the US to do his 737 endorsement a couple of months ago. He had all the right paperwork, including letters from the airline, the course provider, consulate etc.
Upon arrival, he was searched, flying docs found, he produced the letters, but to no avail. Searched again, locked in a room with illegal immigrants, then handcuffed and frogmarched thru the LA apt to the next Qantas flight departing to Aus (they rang and moved forward his return ticket date) and sent to Auckland NZ.
He was not allowed a phone call in LA, nor any consular access. The first access he had to a phone was in Auckland. The US Embassy in Australia confirmed that ALL his documentation was in order.