Warren Buffett and Greg Abel during the Berkshire Hathaway Annual Shareholders Meeting in Omaha, Nebraska on May 4, 2024. CNBC Berkshire Hathaway added a sizeable stake in Delta Air Lines , marking the conglomerate's return to the airline industry after exiting the sector entirely during the Covid-19 pandemic in 2020. The Omaha-based company built a position worth more than $2.6 billion, making Delta Berkshire's 14th-largest holding at the end of March, according to a new regulatory filing. Warren Buffett stunned investors six years ago when he sold Berkshire's entire equity portfolio of U.S. airlines, including stakes worth more than $4 billion across United ,  American ,  Southwest  and Delta Air Lines. Buffett said at the time that the pandemic had fundamentally altered consumer behavior and travel patterns. Among Berkshire's largest holdings, the firm trimmed its stake in Chevron during the quarter while significantly increasing its relatively new position in Alphabet .…