Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What year was the aircraft retired when it was replaced by 737-300s?

### Inputs:
table_name: table, columns: ['Aircraft', 'Introduced', 'Retired', 'Seating', 'Notes']

### Response:
SELECT Retired FROM table WHERE Notes = replaced by 737-300s