When people in the U.S. think about flying, Delta Air Lines (DAL 0.74%) and United Airlines (UAL -1.01%) might be the first companies that come to mind. They both have large market capitalizations and many travelers have flown with one or the other, but they employ very different strategies. Because of this difference, investors can tell which airline is truly first-class.

Different tracks

United CEO Scott Kirby is betting on initiatives such as adding planes and making upgrades like better in-flight Wi-Fi. I like this plan, but it also has risks. Operational mistakes, rising labor costs, and headwinds in other countries are cutting into United’s profits.

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Delta, led by CEO Ed Bastian, is acting differently. Instead of rushing to get more planes, Delta is focusing on making customers happier and being careful with money. The airline is investing in things like Delta Concierge AI, which is supposed to make travel feel more personal and smooth. Its business model counts on premium seats and loyalty programs. Almost 60% of Delta’s money now comes from these sought-after seats and perks.

Delta is often ranked high in customer surveys and for being on time. This good reputation helps it avoid the price wars that can quickly hurt profits in the airline business.

A cleaner balance sheet

Airlines traditionally carry a lot of debt, but Delta is different here, too. In the most recent quarter, Delta had about $16 billion in net debt, equating to a 30 net-debt-to-enterprise-value ratio (which shows how much of the business’s value has been financed with debt). This is quite a lot, but it is less than United’s $18 billion, which gives it a 36 net-debt-to-enterprise-value ratio.

This difference is important. Delta has its best credit rating in years, and leaders have said that controlling debt is a main goal. United, on the other hand, has more debt, which makes it riskier if fuel prices go up, travel decreases, or international expansion plans run into hiccups and the business is pressured.

Hubs vs. horizons

The two airlines also use their networks differently. Delta has strong hubs in cities such as Atlanta, which allow it to group flights together and run its operations smoothly. United is more focused on international growth, which could be beneficial if everything goes well, but it is more complex and risky. Recent global issues, including tariffs and travel restrictions have revealed how fragile this type of growth can be.

By the numbers

The financial results confirm the story. Delta regularly has higher operating and profit margins than United, and it still manages to increase revenue at a steady rate. It also makes more free cash flow, which is needed for a company to pay down debt and give money back to shareholders. Delta’s stock yields about 1.3% at current prices, while United does not pay a dividend.

Even with its stronger financial base, Delta’s stock is slightly cheaper than United’s. Delta’s valuation is about 6.9 based on enterprise value to earnings before interest, taxes, depreciation, and amortization (EBITDA), compared to 10.6 for United. Investors are paying less for a company that makes more reliable profits and is better managed.

What matters for investors

United’s growth plan sounds exciting, and it might work if international markets do well and its operations run smoothly. But there are a lot of risky ifs. For investors who want more reliable returns, Delta’s mix of reliability, profits, and a strong financial base makes it a safer choice.

Delta could be harmed by rising fuel prices, labor disputes, or a decrease in travel. But compared to United’s game plan, the company seems better prepared to handle potential complications without causing trouble for shareholders.

If you had to pay more for a dollar of earnings from either of these airlines, which would it be: The one pursuing growth with a lot of debt, or the one quietly producing higher margins, happier customers, and a stronger financial base?

For me, the choice is clear. Delta isn’t just another airline stock — it’s the first-class option in the sector.