Warren Buffett, who turns 90 in 4 months, had an unpleasant surprise for the permabullish Berkshire faithful during their annual pilgrimage to Omaha live-stream of Berkshire's annual meeting: one month after Berkshire surprised investors by selling parts of its Delta and Southwest Airlines stakes - both of which had previously been above a 10% ownership level and speculation was rife that Berkshire could purchase an airline outright in the near future - the Oracle of Omaha said that, 4 years after Berkshire took major stakes in the four largest US airlines, he had liquidated the sold the entirety of its equity position in the U.S. airline industry which included $6.5 billion worth of stock in United, American, Southwest and Delta Airlines.