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

### Instruction:
When was originally aired the episode with an audience of 1.57 million us viewers?

### Inputs:
table_name: table, columns: ['Series no.', 'Season no.', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']

### Response:
SELECT Original air date FROM table WHERE U.S. viewers (millions) = 1.57