Check out the companies making headlines after the bell:

United Airlines shares jumped as much as 6 percent following a strong top and bottom line beat for the airline's fourth-quarter earnings report. United turned in a profit of $2.41 a share for the most recent quarter, better than the $2.04 a share expected by Wall Street. The airline also gave a forecast for first-quarter earnings of $1 a share, topping analyst estimates of 84 cents a share.

Snap shares fell more than 8 percent after the company announced that CFO Tim Stone is resigning to pursue other opportunities. He joined the company in May. The company also said it expects fourth-quarter results to come in near the top end of its guidance. Snap is scheduled to report those results on Feb. 5.

Apple launched three smart battery cases for its latest generation of iPhones. The tech giant's new offerings can be ordered now and Apple says they will be available to purchase in stores on Jan. 18.

PG&E Corporation shares dropped as much 8 percent, continuing to to crater after closing down more than 17.5 percent in trading Tuesday. The utility lost longtime board director Roger Kimmel, with PG&E's stock adding to its losses of more than 80 percent over the last three months. The massive California utility is facing bankruptcy after its alleged part in helping spark a wave of historic wildfires in California.

Petrobras reported fiscal year 2018 production of 2.6 million barrels of oil and gas per day. The Brazilian energy giant projects in 2019 it will grow that total oil and natural gas production to 2.8 million barrels per day.

— CNBC's Christine Wang contributed to this report.