J.B. Hunt Transport Services (NASDAQ: JBHT) shares fell 13.3% on Wednesday, Sept. 16, after the company warned investors that rising diesel and driver costs would reduce third-quarter earnings.

The S&P 500 fell 0.44%, and the Nasdaq Composite slipped 0.01%.

J.B. Hunt expects earnings to fall 5%–10% in the third quarter

J.B. Hunt, a major trucking and freight company, told investors that they should expect the company to show reduced earnings in its next quarterly update. That's due to $25 million in "additional driver expenses" and $10 million or more from rising fuel prices.

Driver expenses include things like recruiting and training, as well as the signing bonuses drivers often receive.

Diesel costs are rising faster than surcharges can adjust

The company passes the cost of fuel onto its customers, but the surcharges are delayed. That means J.B. Hunt is left paying the bill until the fees catch up. So, the good news is that these costs are temporary and can work in the opposite direction once diesel prices retreat.

Image source: Getty Images.

The warning interrupts a strong freight recovery

This is really a short-term hit, and long-term investors should look past it. These costs are likely temporary and actually signal rising demand, especially the additional training and recruiting costs. Last quarter, revenue rose 19% year over year to $3.5 billion.

However, there's a big asterisk here. If fuel prices don't retreat, trucking could be hit by a slowdown in demand as consumers tighten their belts.