CREATE TABLE table_1291 ("Airline" TEXT, "ICAO" TEXT, "IATA" TEXT, "Callsign" TEXT, "Commenced operations" FLOAT, "Fleet size" FLOAT, "Headquarters" TEXT)

How large is the fleet size of the airline with the IATA code of 5j?
SELECT COUNT("Fleet size") FROM table_1291 WHERE "IATA" = '5J'
SELECT COUNT("Fleet size") FROM "table_1291" WHERE "IATA" = '5J'