James Martin/CNET

When you run the largest social network in the world, security is a big priority.

Facebook said Friday that it spent more than $7.3 million on personal security for CEO Mark Zuckerberg last year, according to an SEC filing. That's up almost 50 percent from 2016's $4.8 million.

The company also said it spent more than $1.5 million on private plane costs, up from $870,000 the year before. Those numbers include payments to the charter company such as passenger fees, fuel, crew, and catering costs, the filing said.

There's likely good reason for the spike in security and air travel costs. Zuckerberg spent last year crisscrossing the country to visit every US state he hasn't visited before -- 30 in total. The trip was one of Zuckerberg's annual personal challenges, basically New Year's resolutions on steroids. In past years, he's vowed to learn Mandarin, build an artificially intelligent digital assistant for his home, and eat only meat he's personally killed.

The company said it's important to invest in Zuckerberg's safety.

"Facebook's board of directors believes that this investment in Mark's personal security is entirely justified," a spokeswoman said. "He is central to Facebook's future success and as founder and CEO of the company has a high public profile."

The SEC filing comes ahead of Facebook's annual shareholder meeting, set for May 31. It also comes after an intense week for Facebook; Zuckerberg testified before two congressional panels, one on Tuesday, the other on Wednesday, over user data and privacy.

Another tidbit from the filing: Zuckerberg still earns just $1 a year, much like Steve Jobs did when he ran Apple. But his compensation for the year was $8.9 million, which includes the security and travel costs.

Just because he technically made only $1 last year, that doesn't mean he's poor. Zuckerberg owns 401.5 million shares of Facebook stock, currently worth $6.6 billion. In fact, he's the fifth richest person in the world, according to Forbes.

First published April 13, 4:06 p.m. PT

Update, 6:17 p.m.: Adds comment from Facebook.

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