Berkshire Hathaway Inc. has increased its stakes in Delta Air Lines and Alphabet, signaling that new Chief Executive Greg Abel is starting to deploy the conglomerate's enormous cash reserves.

According to a regulatory filing released on Friday, during his second full quarter as CEO—succeeding legendary investor Warren Buffett—Abel purchased an additional 17.5 million shares of Delta Air Lines, boosting the value of that holding to $5.37 billion by the end of June. Abel also added 48.1 million shares of Alphabet, propelling the tech giant to become Berkshire's third-largest equity position, valued at $37.8 billion at mid-year.

When Berkshire reported its second-quarter earnings last week, the company disclosed that it had spent approximately $4.5 billion on share buybacks during the period. Additionally, it made net purchases of nearly $20 billion in other stocks. As of June 30, the company's cash pile stood at $365.5 billion, a decrease from the record $397 billion held at the end of March.