What happened

Two days ago, The Wall Street Journal told investors to expect "strong results" from trucking companies enjoying "the most robust freight market in a generation."

Within 24 hours, trucking company Werner Enterprises (NASDAQ:WERN) delivered on that promise, reporting quarterly earnings of $0.53 per share, and adjusted earnings of $0.61; both numbers easily surpassed Wall Street analysts' predictions that Werner would earn $0.50.

So naturally, Werner shares are down today: 11.6% as of 3:15 p.m. EDT.

Semi truck rolling downhill

Werner hit a high note in Q2, but investors wonder when things will start to go downhill. Image source: Getty Images.

So what

Does that seem not to make sense? After all, Werner not only beat on earnings, but on sales as well, reporting quarterly revenue of $619.1 million that eclipsed projections for $587.8 million. Sales climbed 19% year over year for the quarter, and profits were up a whopping 65%.

So what has investors so concerned? Perhaps it's the fact that Werner, which already has one of the newest truck fleets in the nation (its average truck age is under two years), says it's going to spend much more on a lot of new trucks this year. Already, capital spending at the company in the year's first half has nearly tripled from the $66 million spent in last year's H1. In its report, Werner promised to keep its checkbook open and continue spending, ending this year with capital expenditures of anywhere from $325 million to $375 million.

All that spending left Werner with only $7.6 million in actual free cash flow after the first six months of 2018, a 93% reduction from the $112.5 million generated in last year's first half.

Now what

On top of that, Werner also raised fears of higher expenses. On salaries, the company said, "The driver recruiting market is increasingly difficult [and the company will be] raising driver pay." On fuel, it noted that "Diesel fuel prices were 65 cents per gallon higher in second quarter 2018 than in second quarter 2017."

A tight market for shipping did wonders for Werner's financials in the second quarter -- but now that its suppliers and drivers want their pieces of the pie, investors are starting to wonder how much longer the good times can last.