CREATE TABLE table_40827 ("AIRLINE" TEXT, "ICAO" TEXT, "IATA" TEXT, "CALLSIGN" TEXT, "COMMENCED OPERATIONS" TEXT)

What is the callsign where the ICAO is AAR?
SELECT "CALLSIGN" FROM table_40827 WHERE "ICAO" = 'aar'
SELECT "CALLSIGN" FROM "table_40827" WHERE "ICAO" = 'aar'