user: Question: When did 6.09 million people in the US see the original airing of an episode of the show?
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '"Pilot"', 'Ron Hughart', 'Seth MacFarlane , Mike Barker & Matt Weitzman', 'February 6, 2005', '1AJN01', '15.10']
SQL:

assistant: SELECT "Original air date" FROM "Table" WHERE "U.S. viewers (millions)" = '6.09';