Berkshire Hathaway owned and operated by billionaire investor Warren Buffett aggressively purchased stocks during the fourth quarter of 2016 as it close to quadrupled its stake in tech giant Apple and increased stakes by sevenfold in four of the largest airlines in the U.S.

In a filing with regulators, Berkshire posted ownership of 57.3 million Apple shares as of December 31, which would be worth at this time more than $7.74 billion, which is up from its 15.2 million Apple shares from the prior quarter.

The company reported as well a stake of $9.3 billion in airlines, with investment exceeding $2.1 billion in each of Delta Air Lines, American Airlines, United Continental and Southwest Airlines.

It disclosed as well new stakes it holds in Sirius XM Holdings a satellite radio business and Monsanto the seed company, which Bayer AG in Germany recently acquired.

Though it is not clear who made which investments, Berkshire’s filing appears to reflect a great deal of the stock of $12 billion that Buffett said he purchased between the presidential election of November 8 and January 31.

Larger investments of Berkshire such as Coca-Cola, IBM and Wells Fargo are Buffett’s, but the billionaire, who is 86, had handed his deputies Ted Weschler and Todd Combs more money to invest the past few years.

Berkshire’s first investment with Apple received attention in 2016 given the usual aversion by Buffett for tech companies, with the exception of IBM, which he says are outside his competence zone.

The larger stake now makes Berkshire one of the top 10 largest investors in Apple.

One analyst, who oversees shares of Berkshire for a financial house said he was stunned at the size of Berkshire’s position in Apple.

Berkshire, based in Omaha, Nebraska, owns close to 90 companies including Dairy Queen, Geico insurance and BNSF railroad.

Its shares of Class A on Tuesday closed higher.

The increase in stake in Apple appears to be timed well. Apple shares were up Tuesday $1.73 which was also a record high at close for the tech company.

Assuming no part of Berkshire’s stake has been sold, Apple’s 16.6% gain in 2017 would leave Berkshire with a paper profit for just 2017 of $1.1 billion.

Most believe the initial investment by Berkshire in Apple was by Weschler or Combs. However their decisions are known to be influenced at times by Buffett.