CREATE TABLE table_1317 ("Episode" FLOAT, "Title" TEXT, "Story" TEXT, "Adapted by" TEXT, "Director" TEXT, "Airdate" TEXT, "Exists?" TEXT)

What is the airdate when the director is george spenton-foster
SELECT "Airdate" FROM table_1317 WHERE "Director" = 'George Spenton-Foster'
SELECT "Airdate" FROM "table_1317" WHERE "Director" = 'George Spenton-Foster'