It's time to get worried about the US economy - according to the people who know best

UPS was just the icing on the cake.

Capping off a week of gloomy commentary from American companies, the package-delivery giant - which arguably has a unique view into the global economy - said it too sees "head winds" in the second half of the year.

Like others that warned about a slowdown, UPS reported on-target earnings and kept its forecasts unchanged. But that's because of "technology and productivity investments" that are helping it manage through.

Its shares fell a little. Ford on the other hand lost 10% of its market value after it cautioned that carmakers were getting aggressive with incentives to lure in buyers - a sure sign that one big economic engine, auto sales, are peaking. Shares of other carmakers fell too.

That wasn't all. American Airlines said it expects ticket prices to fall. Why? Because "if there is a business confidence problem, the first thing businesses do is cut entertainment and travel budgets," President Scott Kirby said during the company's earnings call.

Even some of the good news isn't such great news.

Banks like Goldman Sachs and Citigroup did better than expected. But that's because there's more trading going on right now as investors try and get a handle on uncertainty surrounding the global economy. Britain's unexpected decision to leave the EU, for example, had traders scrambling at the end of the quarter.

And although oilfield-services giants like Halliburton and Schlumberger both called a bottom on the oil market's slump, the world's largest manufacturer of industrial equipment - Caterpillar - said it doesn't see anything getting better.

"We're not expecting an upturn in important industries like mining, oil and gas, and rail to happen this year," CEO Doug Oberhelman said. The firm cut its forecast for 2016 earnings, and said it plans to lay off more workers.

The litany of worries just adds to a growing sense that the world's economy is entering a slowdown.

"Earnings season in the U.S. confirms the overall macro picture that we have. We have a global slowdown. It's evident in all of the major economies," said Peter Garnry, head of equity strategy at Saxo Bank, on a Bloomberg podcast.

Confirming what? Well, the July PMI reading - a measure of manufacturing activity - and orders of durable goods both were worse than expected. And then the big report - second-quarter gross domestic product - showed that the US economy is already growing less than anyone expected.

One glimmer of good news (maybe)? The Federal Reserve feels better about things.

"Near-term risks to the economic outlook have diminished," the central bank's policy statement said on Wednesday.

So there's that. But as Credit Suisse noted after the statement, the Fed being "less worried" isn't exactly a sign of great confidence. The bank's economists expect no interest-rate increases this year.

Garnry puts the good news coming out of some companies down to low expectations and paints a picture of overall weakness.

"The outlook is still very clouded," he said. "I'm not sure this earning seasons is giving us the clarity that we had hoped for."