In my past experiences, I've always had a business visa to transit through with. Basically if you get off the airplane at LOS, you WILL be going through customs. LOS does not have any way to corral people back upstairs and into any sort of intl waiting area. Yellow Fever card must be in your hand exiting the jetway as well.

Ottawa Website Says:
http://www.nigeriahcottawa.com/visit...sit-vbt-9.html

New York Website Says:
http://www.nigeriaembassyusa.org/ind...a-requirements

They do make note of a transit visa is this embassy webpage for Canada, but no where on the US site do they talk about it. I'm a US citizen living and working in Canada, travelling on a US Passport, so all my filings go through Ottawa as a foreign citizen.

If you don't get off the plane and have a contiguous itin, I wouldn't worry. If you getting off the plane, I'd be sure to maybe call your local consular office and find out for sure. Because once you're in front of those guys, they got ya by the short and hairy's.

Accra is a good example on UA IAD-LOS. The stopover in ACC, they make you get off the plane, corral you right back into a waiting area, and you never have to deal with a customs officer. They put you back on the plane and it's like you never landed in country.

ironmanjt knows his stuff though...

...just my two cents ;-)