The only OW carrier that flies to PPT in its own metal is LA. The route is SCL-IPC-PPT. So to get there from SEA, you'd need to do an AA-LA combo on a routing looking something like SEA-DFW-SCL-IPC-PPT. It might be quicker for you to try to get to AKL or SYD and then go up to PPT on a paid flight?