Originally Posted by
VidaNaPraia
For domestic flight in Brazil, you can even check in only an hour beforehand. Lines are usually not as long or as slow-moving as in the U.S. for example.
This site may have some info you can use for the wee hours at GIG:
http://www.sleepinginairports.net/casa/riodejaneiro.htm
OP will, of course, be on an international fight. I've been in quick-moving and slow-moving lines at Brazilian airports. Luck of the draw (e.g., staffing at that particular time, number of passengers with complaints or unusual situations, or large numbers of bags).