• Stocks are up for the shortened holiday week, with the Nasdaq the biggest winner.
• Nippon Steel extended the closing date for its acquisition of U.S. Steel as President Joe Biden decides whether to block the deal.
• From the Boeing door panel malfunction to Spirit's bankruptcy filing, airlines had an eventful year.

Here are the most important news items that investors need to start their trading day:

1. Green Christmas

Investors hope stocks will close the holiday shortened week strong. While trading has been sparse, the three major U.S. averages have all climbed this week. The S&P 500 has gained 1.8%, the Dow Jones Industrial Average has ticked 1.1% higher and the Nasdaq Composite has jumped 2.3%. It follows stronger performance for the tech-heavy index throughout the month. The Nasdaq has gained 4.2% so far in December, versus a 0.1% increase for the S&P and 3.5% decline for the Dow. Follow live market updates.

2. Steeling for a decision

Nippon Steel said it has pushed back the closing date for its $14.9 billion acquisition of U.S. Steel, as President Joe Biden decides whether to allow the deal to go through. The Japanese company changed the date to close the acquisition to the first quarter of 2025, from a previous target of the third or fourth quarter of this year. A committee that oversees foreign acquisitions in the U.S. referred the decision on whether to block the deal to President Joe Biden on Monday, giving him 15 days to decide. Biden, the United Steelworkers union and some politicians have raised concerns about foreign ownership of the company.

3. Holiday balances

Holiday shopping could have long-term consequences for many consumers. Thirty-six percent of Americans took on debt this holiday season, according to a LendingTree survey. The average balance among those people was $1,181, up from $1,028 in 2023. Starting early to pay down debt and renegotiating interest rates are among the ways to chip away at holiday debt.

4. Airlines' wild year

Airlines started off the year with a door panel blowing off of a Boeing airplane during an Alaska Airlines flight. The headlines didn't slow down from there. The JetBlue-Spirit merger was blocked, Spirit filed for bankruptcy protection and a tech meltdown affected days of travel. Meanwhile, carriers fought to show they were the most premium airline. Read more about an eventful 2024 for airlines here.

5. Adding up

Ad executives expect the market to stabilize next year, especially for the companies that have coveted live sports rights. The worldwide advertising industry is expected to grow 7.7% and top $1 trillion in revenue in 2025 for the first time, excluding U.S. political ads, according to a recent report from GroupM, WPP's media investment group. Even so, advertisers may still be selective with their budgets, and are prioritizing live events like sports and awards shows.

– CNBC's Pia Singh, Lorie Konish, Leslie Josephs and Lillian Rizzo contributed to this report.