1. After the gates to the luggage area are opened, you have to run to the second 
floor to operate a control panel. There is an office right before the control 
panel. Search around the back of the office to find the briefcase.

2. On the third floor of the SSC tower where you have to jump onto the lift, 
ignore the lift, and keep running forward to the back of the floor to find the 
briefcase. It is directly opposite and across to the staircase that you came up on.