The stock market moved lower on Thursday morning, investors watching nervously as an outbreak of coronavirus in China raised global health concerns. Market participants worry that the disease could disrupt economic activity if it becomes widespread, and Chinese stocks in particular were weak as investors mulled over the potential business implications. As of 11:20 a.m. EST, the Dow Jones Industrial Average (DJINDICES:^DJI) had fallen 180 points to 29,006. The S&P 500 (SNPINDEX:^GSPC) dropped 15 points to 3,307, and the Nasdaq Composite (NASDAQINDEX:^IXIC) lost 20 points to 9,364.

We're currently near the peak of earnings season, and the readings thus far have been mixed. Southwest Airlines (NYSE:LUV) managed to post modest gains despite some discouraging numbers in its most recent quarterly report, but Union Pacific (NYSE:UNP) got the benefit of more favorable results.

Southwest deals with more MAX concerns

Shares of Southwest Airlines were up between 1% and 2% in the wake of the airline's fourth-quarter financial report. That came despite a drop in Southwest's bottom line, and even with the rise in share price, investors still aren't entirely sure how to get past concerns about the future of the 737 MAX aircraft.

Southwest painted aircraft on ramp approaching runway at desert airport.

Image source: Southwest Airlines.

Southwest's net income for the fourth quarter fell 21% from year-ago levels, although much of the drop came from higher profit-sharing contributions to employee compensation. Revenue inched higher by 0.4%, although both passenger and freight-related sales posted modest declines. Despite cheaper fuel costs, total operating expenses rose significantly.

CEO Gary Kelly was quick to note that Southwest's performance throughout 2019 was "truly remarkable," given the impact of the grounding of the 737 MAX for much of the year. Yet the airline wasn't able to reassure investors about any firm timeline for a return to service for the aircraft, saying only that it's already adjusted schedules through early June. Other airlines are looking at even longer delays for the 737 MAX.

Southwest gets big benefits from operating only 737 aircraft models, but it's proven to be a big problem for the airline in light of the MAX's issues. For now, shareholders are optimistic that things will turn out well, but only time will truly tell whether 2020 will be a bounce-back year for Southwest.

Union Pacific stays on the tracks

Meanwhile, shares of Union Pacific moved higher by 2%. The railroad giant reported solid results in the fourth quarter, and even though industry conditions remain tough, investors have high hopes that long-term strategic moves will pay off for the rail transportation and shipping company.

Union Pacific saw operating revenue fall 9% on an 11% drop in carload volumes. Transportation of energy products delivered the biggest volume hit, sending freight revenue for the segment down 25% from year-ago levels. Industrial and agricultural shipments held up somewhat better, but there wasn't any true growth across the railroad's business segments.

CEO Lance Fritz kept a long-term perspective, noting that the railroad is still on track with its strategic plan and has boosted efficiency even as shipment volumes remain weak. An emphasis on safety hasn't stopped Union Pacific from improving train velocity and waiting times.

Union Pacific's stock has climbed to new highs in the past couple of months, reflecting optimism about the U.S. economy and global trade. Now, it'll be up to the railroad to make the most of any opportunities it gets to grow.