Landstar System stock fell 16%, marking its worst day ever|Seth Granville|CC BY-NC 2.0

Trucking and logistics stocks suffered one of their worst days ever on Thursday after a tiny Florida company, Algorhythm Holdings, spooked investors with big claims about artificial intelligence.

The firm that previously sold karaoke machines said its AI software, SemiCab, could cut empty truck miles and boost freight capacity by 300% to 400% without increasing headcount. 

Even though Algorhythm has no major US customers and a market value below $3 million, its claim sent shockwaves, and investors quickly hit the sell button:

The broader Dow Jones Transportation Average fell 4%, with 17 of 20 companies down, erasing $17.4 billion in value.

Healthcare distributors McKesson and Cardinal Health each lost more than 4%, showing the fear spread beyond trucking.

Analysts later called the selloff exaggerated, highlighting how quickly AI hype can shake markets.