I recently got back from my vacation to Costa Rica. Instead of going on American’s or Delta’s website and inputting SEA->SJO like a normal person, I ended up booking 6 different legs, on 2 different airlines. Here are the legs for the trip:
SEA->BWI on Alaska
BWI->ATL on Delta
ATL->SJO on Delta
SJO->ATL on Delta
ATL->BWI on Delta
BWI->SEA on Alaska