user: Question: What was the original air for the 06-03-521 production code?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [86.0, 1.0, '"Vegas"', 'Bryan Cranston', 'Michael Glouberman & Andrew Orenstein', 'November 2, 2003', '06-03-501']
SQL:

assistant: SELECT "Original air date" FROM "Table" WHERE "Production code" = '06-03-521';