Hi,
I am on a L1 visa. I entered US last year november-2008.

I am not sure whether I would be considered a non-resident alien or a resident alien for the purpose of filing tax in 2009.

If I am considered a non-resident alien, will I become resident alien after(six months) if I file for an exention to file tax.

-ss

You can file the extension and file as a resident alien ONLY IF you are married.

If you are single, you should file as a non-resident alien, filing Form 1040NR or 1040NR-EZ.