US Transit visa - C1 general visa

[skorpian_guy]

Hello,

I have a situation and wanted to know if any one is aware/experienced the same situation.

I am going to Canada (Vancouver) US Embassy to revalidate my visa. On the safer side, I booked an appointment with Chennai consulate and I am travelling to India directly from Vancouver after getting my visa.

For any reason, if my visa is not issued at Vancouver, I will be catching the flight to India anyway. And my flght from Vancouver has a stop at Los Angeles.

If I dont have my visa revalidated, as I will be transiting through US, I guess I need to apply for Transit Visa (C1 general).

My question is can I get that transit visa in LA airport when I get down? Or do I need to apply for C1 (transit) visa prior to my travel and get an appointment with US embassy and proceed etc. etc..

Almost all the immigration sites including travel.state.gov doesnt have any mention about if one can get the transit visa at the airport in US who doesnt have it already.

Can any one of you or your parents/in-laws travelled through US without a prior Transit Visa?
Is there any site where I can get clear details about this?

Your help is much appreciated.

Thanks
San