STORY: Big banks kicked off the U.S. corporate earnings season Friday with a mixed bag of results.

JPMorgan Chase beat estimates for second-quarter profit as its investment banking business benefited from a resurgence in dealmaking.

CEO Jamie Dimon said that while the economic outlook was (quote) "benign," the bank continues to be "vigilant about potential tail risks."

JPMorgan shares were trading lower Friday morning.

Shares of Wells Fargo slid more than 6% as the lender missed estimates for quarterly net interest income - the difference between what a bank earns on loans and pays out for deposits.

Meanwhile, Citigroup posted a 60% surge in investment banking revenue and reported gains in its services division.

But shares fell more than 2% as investors saw challenges for Citi broadening market share and reducing its expenses.

Analysts have called 2024 a transitional year for Citi, as CEO Jane Fraser carries out a sweeping overhaul of the bank in an effort to improve its performance and cut costs.

Declining bank stocks pushed the S&P 500 Financials Index lower, while the banks index, down more than 2%, was on track for its biggest single-day slump in nearly two months.