Originally Posted by qfrodo

Not sure why, if you are arriving on UA, you aren't continuing on to GIG on UA. If coming from ORD, it connects to UA 861 (from IAD)

Whatever the reason, when one deplanes UA and they are connecting to GIG there will be an agent directing the continuing passengers into the waiting area. So you could probably do this. Occasionally they have to do a hard stand on the tarmac and bus people to the terminal. In that case, you can still be directed to the waiting area for the next flight, but may have to go through security. However, will you have the boarding pass for the TAM flight? If not, it could lead to difficulties. Perhaps others can tell you if you can get a JJ BP at the gate. Haven't read about anyone doing what you indicate, so you might be the guinea pig