Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Commercial transportation specialist Forward Air (Nasdaq: FWRD) was spinning its wheels today, dropping 11% today after management cut third-quarter guidance.

So what: The quarterly forecast was cut sharply, down from a range of $0.47 to $0.51 a share to a range of $0.39 to $0.41, well below the average estimate of $0.49. CEO Bruce Campbell said the quarter had started off strongly but that airport-to-airport tonnage began to decrease in August. A rate increase imposed on September also failed to deliver the results he had expected.

Now what: Forward Air's announcement echoes Fed Ex's (NYSE: FDX) decision last week to cut its full-year outlook by about 10%, as the shipping king said the global economy is slowing. Caterpillar (NYSE: CAT), another bellwether for the global economy, also sent negative signals yesterday. With management making this announcement right as the quarter is ending, investors may want to play it cool. If the heavyweights are right about the cooling of the economy, Forward Air could be forced to cut guidance again in Q4. Right now, analysts are calling for $0.58 a share in the last three months of the year.

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