What happened

Macquarie Infrastructure (NYSE:MIC) stock is plummeting in Thursday-morning trading after the company reported Q4 earnings last night. Backing out one-time gains and losses, Macquarie said it earned $0.45 per share (pro forma) last quarter, better than the $0.33 that Wall Street analysts had predicted. Q4 revenues of $437.8 million, however, fell short of the $453.4 million Street consensus.

Macquarie Infrastructure shares are down 9.7% as of 11:50 a.m. EST in response.

Oil storage tanks.

One of Macquarie's biggest businesses is simply holding oil in tanks until someone has a need for it. Image source: Getty Images.

So what

It gets worse. Although Macquarie would probably prefer investors to focus on its pro forma results, the fact remains that when calculated according to GAAP accounting standards, Macquarie actually lost $3.8 million last quarter -- about $0.01 per share, versus the $4.19 per share profit that it earned in Q4 2017. And even the company's net income from continuing operations declined 85% year over year in the absence of the tailwind provided by last year's tax reform in the U.S., which boosted Q4 2017 profits.

Check out the latest Macquarie earnings call transcript.

Now what

Adding to Macquarie's troubles, analysts at RBC Capital are panning the company's just-released fiscal 2019 guidance (and downgrading Macquarie's stock), saying guidance implies "further deterioration" in the company's International-Matex Tank Terminals business. For 2019, Macquarie told investors to expect "consolidated EBITDA of $610.0 to $635.0 million" (but gave no GAAP guidance) and "free cash flow of $400.0 to $445.0 million."

Investors aren't responding well to that news. However, I note that in 2018, Macquarie's free cash flow was only $342 million, as calculated by S&P Global Market Intelligence. Should Macquarie succeed in generating between $400 million and $445 million in cash profit this year, at the midpoint, that would work out to better than 23.5% FCF growth.

That's a very respectable growth rate if you ask me. With Macquarie stock only costing about 10 times FCF after today's sell-off, it could be that Macquarie investors are selling their shares too soon.