1496    Leonardo da Vinci unsuccessfully tests a flying machine.

1963    Leonardo da Vinci's ''Mona Lisa'' is exhibited in the United States for the first time, at the National Gallery of Art in Washington, D.C.

1967    American researchers discover the Madrid Codices by Leonardo da Vinci in the National Library of Spain.

1999    In Milan, Italy, after 22 years of restoration work, Leonardo da Vinci's masterpiece ''The Last Supper'' is put back on display.