The Dow Jones Industrial Average ended another volatile week lower Friday, but not before the blue-chip index notched its best weekly gain since 1938, as President Donald Trump was set to sign into law an important coronavirus rescue package just after the market's close. The Dow /zigman2/quotes/210598065/realtime DJIA -0.07% fell 915 points, or 4.1%, at around 21,636, the S&P 500 index /zigman2/quotes/210599714/realtime SPX +0.48% closed 89 points, or 3.4%, at 2,542, while the Nasdaq Composite Index /zigman2/quotes/210598365/realtime COMP +1.29% ended the session down 3.7% at around 7,502. For the week, the Dow booked a gain of 12.8%, which marks its best weekly gain since 1938, according to FactSet data. The S&P 500 notched a weekly gain of 10.3%, representing its sharpest weekly rise since 2008, while the Nasdaq Composite Index booked a 9.1% weekly gain. In addition to the fiscal response, the week was marked by the Federal Reserve announcing an unlimited bond-buying program to loosen seized up parts of the financial markets. All these factors helped to boost the market but deep-set worries about when he virus will ultimately peak as investors worried. Trump's planned signing of the coronavirus relief package would follow news that the U.S. has become the country with the highest number of COVID-19 cases. It also comes after a record 3.28 million Americans applied for unemployment benefits last week due to the outbreak, earlier in the week, highlighting growing signs of the impact of the deadly infection. The turbulent week also saw the Dow and the S&P 500 notch three straight days of gains, until Friday, as investors cheered the planned fiscal measures by the U.S. government. Moves in the Dow were aided by a comeback for the ages from blue-chip component Boeing Co. /zigman2/quotes/208579720/composite BA -2.65% which surged 70.5% for the week, marking its best weekly gain ever, according to Dow Jones Market Data. The aeronautics maker has been hammered by the slowdown in travel and the grounding of its 737 MAX fleet of jets.