Originally Posted by
planemechanic
As a dual citizen I have to always enter/exit from my "home country" on my "home country" passport. So I enter/exit the US on my US passport and enter/exit the UK on my UK/EU passport. Each country that you have a passport with generally require that you enter/exit the country on their passport.
As far as the immigration officer not seeing stamps I have never had a problem with that.
This is okay if you can enter the destination country with a US passport w/o a visa.
If you exit the US with a US passport (what does that mean?) then the airline might not let you on the aircraft to Brazil w/o a visa. If you exit with a Brazilian passport, then, well, I dunno...