CREATE TABLE table_21433 ("Episode Number" FLOAT, "Air Date" TEXT, "Event 1" TEXT, "Event 2" TEXT, "Event 3" TEXT, "Event 4" TEXT)

On how many different dates was event 1 Suspension Bridge?
SELECT COUNT("Air Date") FROM table_21433 WHERE "Event 1" = 'Suspension Bridge'
SELECT COUNT("Air Date") FROM "table_21433" WHERE "Event 1" = 'Suspension Bridge'