关于去美国在加拿大转机是否需要过境签的问题

helio5

I have done a lot of research work on this issue.Some ppl are discussing this problem in this forum. So, I guess that sharing what I know can be helpful.

First, pls read these two page:

http://www.aircanada.com/en/news/110328.html
http://www.cbsa-asfc.gc.ca/travel-voyage/twov-tsv/cct-pptc-eng.html

According to above information, the program, China Transit Trial, allows some qualified Chinese passengers to transit without having to obtain a Canadian transit Visa.

However, there is an issue that I am confusing. When a passenger arrives after the U.S. in-transit pre-clearance facility is closed, what will happen?
According to CBSA, travelers must proceed to a CBSA officer for examination. I don't what it means. What is the working hour of US in-transit pre-clearance facility? How long it will take? If it takes a lot of time, people could miss their next flight.