Although plane and bus timetables are kept to whenever possible, in the less developed parts of the country - most notably Amazonia but also the interior of the Northeast - delays often happen. Brazilians are very Latin in their attitude to time, and if ever there was a country where patience will stand you in good stead it's Brazil. Turn up at the arranged time, but don't be surprised at all if you're kept waiting. Waiting times are especially long if you have to deal with any part of the state bureaucracy, like extending a visa. There is no way out of this; just take a good book.