The U.S. dollar weakened sharply against the Japanese yen on Monday after Trump and Japan's finance minister confirmed both sides had intervened in markets.
The lawsuit, filed in the Southern District of New York, claims that Robinhood's actions rigged the market against its customers.
The S&P 500 slumped 1.7% as soon as trading began, only to churn through another turbulent session.
Investors have waited a long time for San Francisco-based AirBnb to announce its plans for an initial, public offering.
The Dow Jones industrial average crossed the 20,000 mark for the first time Wednesday, the latest milestone in a record-setting drive for the stock market.
Dow Chemical and DuPont are merging to form a company valued at about $130 billion.
