It is possible to walk from T-5 to T-1 at LAX
-- allow about 20 minutes. If walking, I recommend taking the upper level sidewalk, from which there are lots of great, closeup airside views at the terminals along the way. Or, as AirDD mentions, there is shuttle service that connects all terminals for no charge, running at about 5-minute intervals. To allow for long lines at both check-in and security -- a regular occurance at LAX
-- plan your arrival on Delta to be at least
2 hours before your Southwest departure.