Buffett’s Berkshire Hathaway (BRK-A) nearly quadrupled its stake in Apple (AAPL) in the final quarter of 2016, the company revealed in a securities filing late Tuesday.

That makes Buffett’s insurance and investing conglomerate one of the tech company’s ten largest shareholders, owning more than 1% of Apple stock, a monster holding currently worth more than $7.7 billion. What’s more, it has already been a profitable investment for Buffett. Thanks to Apple’s breakout 17% rise so far this year, Berkshire has already made more than $1.1 billion on the stock in 2017 alone. (Had Buffett not upped Berkshire’s Apple holding, Buffett’s company would only have made $400 million on the shares it previously owned.)

Buffett has been shifting more of the investing responsibilities at Berkshire Hathaway to two investment managers he hired a few years ago, Todd Combs and Ted Weschler. So it is possible that the Apple investment was initiated by one of his two lieutenants. Still, most of the Berkshire’s biggest investment positions are still driven by Buffett, so it is likely that Apple is his stock pick.

Buffett first bought Apple stock about a year ago, in early 2016. At the time, the move marked a shift in strategy for the investor, who has largely steered clear of technology stocks (and doesn’t even own a smartphone).

But the large size of the position, which makes Apple the seventh largest holding of Berkshire Hathaway, signals that Buffett has embraced the iPhone maker for the long haul. After all, Apple, which trades at a valuation lower than the market average and pays a dividend yielding 1.7%, has many of the hallmarks of a quintessential Buffett stock.

In addition to Apple, Buffett also loaded up on a lot more of the airline stocks he first disclosed late last year, expanding his positions in Delta Air Lines (DAL), United Continental (UAL) and American Airlines (AAL) several times over, and adding a more than $2 billion stake in Southwest Airlines (LUV). Shares of those companies jumped in after-hours trading following Buffett’s disclosure, with American Airlines stock rising more than 2%.

Berkshire Hathaway’s stock portfolio also invested in several new stocks, including a position in Monsanto (MON) worth more than $865 million, as well as a $790 million stake in Sirius XM Holdings, the satellite radio company. Still, it was unclear whether Buffett himself had decided to buy those stocks for the first time, or rather the strategy of one of his two deputies.

Sirius XM stock surged more than 3% after-hours, while Monsanto stock rose as much as 1%.

Apple stock, which had gained 1.3% during regular market hours Tuesday, was up slightly more after Buffett’s filing.