CREATE TABLE airport_aircraft (Aircraft_ID VARCHAR2, Airport_ID VARCHAR2)
CREATE TABLE aircraft (Aircraft_ID VARCHAR2, Aircraft VARCHAR2)
CREATE TABLE airport (Total_Passengers NUMBER, Airport_ID VARCHAR2)

What is the average total number of passengers of airports that are associated with aircraft 'Robinson R-22'?
SELECT AVG(T3.Total_Passengers) FROM aircraft AS T1 JOIN airport_aircraft AS T2 ON T1.Aircraft_ID = T2.Aircraft_ID JOIN airport AS T3 ON T2.Airport_ID = T3.Airport_ID WHERE T1.Aircraft = "Robinson R-22"
SELECT AVG("T3"."Total_Passengers") FROM "aircraft" "T1" JOIN "airport_aircraft" "T2" ON "T1"."Aircraft_ID" = "T2"."Aircraft_ID" JOIN "airport" "T3" ON "T2"."Airport_ID" = "T3"."Airport_ID" WHERE "Robinson R-22" = "T1"."Aircraft"