Aetna and Humana just called off their $34 billion merger deal on Tuesday, after a federal judge blocked the deal in January on antitrust grounds. Aetna will pay Humana a $1 billion breakup fee, approximately $630 million after taxes, to terminate the deal, the companies said. If the merger came through, the companies would have left the health insurance industry dominated by only three giant insurers. "While we continue to believe that a combined company would create greater value for health care consumers… the current environment makes it too challenging to continue pursuing the transaction," Aetna chairman and CEO Mark Bertolini said in a statement.