We have also gotten partner mileage tickets online with Alaska air. your confirm page should have confirm codes both for Alaska, American and British airways. go to individual airlines website and enter their code to select seats for flight segment your flying on them. Note British airways will charge you for selecting seats ahead of 24hr check-in (unless in FC). We have also just called the airlines once using their respective codes to see about seat together. They can tell you their current policy of seat selection and cost. Good Luck