According to news reports, a computer problem with a U.S. Customs and Border Protection immigration system delayed more than 20,000 arriving passengers into LAX for hours. The problem began at 1330 local time yesterday, and a back-up system wasn't operational until 2145. The last person finally cleared customs at 0350 this morning. A couple of flights diverted to other airports to avoid the problem.
What is interesting in reading the various news stories was that U.S. Customs and Border Protection authorities were telling the press that initially it was 2,500 and then later 6,000 passengers were affected. In the LA Times article I linked to, you'll see that the airport said that it was 11,000 passengers that were affected but Customs finally ended up with a 20,000 passenger count.
I don't know what is more troubling - the computer glitch or the "lost 9,000."
