Though it is unclear who make which investments, the filing appears to reflect much of the $12 billion of stock that Buffett said he had bought between the November 8 Presidential election and the end of January. The figure climbed in recent quarters because of profit from Berkshire's dozens of subsidiaries and the redemption of securities that Buffett bought to fund deals. Berkshire added to the investments in American and United.

Not all the picks in the portfolio are Buffett's. In 2010, he brought on Todd Combs, a former hedge fund manager, to help him pick stocks. A year later, the billionaire hired another money manager, Ted Weschler. In general, the deputies tend to make smaller investments than their boss.

Buffett told talk show host Charlie Rose in an interview last month that it was "in large part" his decision to dive back into airlines. However, thanks to the rally in the tech giant's shares so far in 2017, the holdings are now worth roughly $7.7 billion, a hefty gain of $1.1 billion in about six weeks of trading.

Warren Buffett is taking a big bite out of Apple.

Buffett's firm invests heavily in Apple, airline stocks

To make room for new investments, Berkshire appeared to have shed a $1.8 billion stake in agricultural equipment maker Deere & Co and almost all of what remained from a more than decade-old stake in retailer Wal-Mart Stores Inc. On Tuesday, the stock's price hit new highs.

Apple gained 0.4 percent and finished at $135.51 on Wednesday. Berkshire also cut its Walmart holdings by 89.3 percent, dissolved its share stake in Now Inc, and increased its holdings of Delta Air Lines to 60 million shares from 6.3 million. During the past two decades, Buffett has focused more on acquisitions than picking stocks.

Berkshire, based in Omaha, Nebraska, owns close to 90 companies including Dairy Queen, Geico insurance and BNSF railroad. Early a year ago, Buffett completed one of his biggest acquisitions, the $37 billion buyout of Precision Castparts Corp., a supplier to the aerospace industry.

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