What year was the aircraft retired when it was replaced by 737-300s?
CREATE TABLE table_name_91 (retired VARCHAR, notes VARCHAR)
SELECT retired FROM table_name_91 WHERE notes = "replaced by 737-300s"
### Context: CREATE TABLE table_name_91 (retired VARCHAR, notes VARCHAR) ### Question: What year was the aircraft retired when it was replaced by 737-300s? ### Answer: SELECT retired FROM table_name_91 WHERE notes = "replaced by 737-300s"