from south there are 2 options:

1st.
Exit C5 then take the U turn after the toll and use the service road up to Gate 3.

2nd.
Exit at NAIA 3 Skyway. Instead of going to the end of NAIA 3 road, I strongly suggest that you turn right after you go down from the skyway ramp then turn right then right again then right until you are at the NAIA 3 road so you could use the first U turn slot. ( pasencya kung magulo, pero mas okay ito kesa pumunta kayo sa dulo ng NAIA 3, matraffic tapos pangit pa kalsada )