They are coming from South Signal Village / New Lower Bicutan.

Someone told me that they can avoid the expressway (including NAIA Expressway) by taking the local streets.
The main issue for them would be that although they are close to T3 they have to drive around as the roads to the terminal only goes one way - they will be coming from the south east of the terminal and the entrance is at the north of the Terminal so they may get caught in the NAIA Expressway traffic flow.