Compared to many CEOs, Apple boss Tim Cook keeps a low profile. But in 2017 he hit a milestone that may be the mark of true celebrity.

Apple’s board implemented a policy in 2017 requiring Cook to “use private aircraft for all business and personal travel” for his safety, according to regulatory filings published on Wednesday.

It’s quite common for a CEO to travel in private jets — GE’s past CEO, Jeff Immelt, apparently had more than one. But even as the leader of the world’s most profitable company, Cook has held out until this year, as last year’s proxy filing doesn’t mention any private flights, just the occasional chartered plane.

Cook doesn’t tend to make many high-profile appearances, but his job does require him to travel to locales like Scotland, China and India, and Apple’s stores and data centers across the U.S.

In 2016, Cook had security expenses of $220,432. In 2017, it was almost identical, at $224,216, but included the addition of personal air travel expenses in the amount of $93,109.

Cook made about $12.8 million in 2017, up from $8.7 million in 2016. He’s still actually the lowest paid among his executive team, who all make around $24 million a year. Then again, Cook does own shares with a value of over 46 times his base salary of $3 million