Wall Street saw negative sentiment return in a big way on Thursday, powering the Dow Jones Industrial Average to a loss of more than 600 points. Despite all the attention that one key player in the tech sector got, declines were spread out across the market, and investors seemed worried overall about the potential for a global economic slowdown that could bring the long bull market in the U.S. to a halt once and for all. Several high-profile stocks suffered big drops, and Delta Air Lines (NYSE:DAL), Atara Biotherapeutics (NASDAQ:ATRA), and Skyworks Solutions (NASDAQ:SWKS) were among the worst performers. Here's why they did so poorly.

Delta sinks on weaker outlook

Shares of Delta Air Lines finished 9% lower after the airline giant reported its operating performance for December and also gave an early look at fourth-quarter financial projections. The carrier said it had a record 15.3 million customers during the month, but investors seemed dissatisfied with Delta's prediction for adjusted earnings of between $1.25 and $1.30 per share, despite it being close to the consensus forecast among those following the stock. Delta did cut its growth estimate for revenue per available seat mile by half a percentage point to 3%, however, and that stoked fears that 2019 might not be as strong a recovery year as some were hoping.

Check out the latest Delta Air Lines earnings call transcript.

White airplane with Delta markings on a clean tarmac under a dark overcast sky near sunset.

Image source: Delta Air Lines.

Atara makes a CEO move

Atara Biotherapeutics saw its stock plunge more than 19% following news that the company will lose its current chief executive officer. CEO Isaac Ciechanover will step down by mid-2019, with the expectation that Atara will name a successor before June 30. Atara saw huge ups and downs in 2018, nearly tripling in value during the first five months of the year but then falling more than 40% between May and December. Many still see plenty of promise for the company's allogeneic cell therapies, but as the market environment turns hostile, shareholders don't seem convinced that Atara will see its stock price bounce back in 2019.

Skyworks deals with lower smartphone sales

Finally, shares of Skyworks Solutions closed lower by nearly 11%. The maker of internet network connectivity chips for smartphones was just one of many companies that fell sharply on news that sales of iPhones would likely come in well below what most investors were expecting to see. Skyworks has been tied to the fortunes of the smartphone market for a long time, and even though it's worked hard to diversify its exposure to include connectivity in autos, wearable devices, and smart-home applications, it still has a long way to go before it can shrug off smartphone weakness completely.

Check out the latest Skyworks earnings call transcript.