Most Turkish Airlines routes between the U.S. and Istanbul are wide open for business class award redemption between October and January – for four or more passengers! – with some routes having availability starting in May.
Turkish is a Star Alliance airline, which means you can use United miles to book. Or you can transfer Citi, Bilt, or Capital One points directly to Turkish for some amazing award pricing. You can also transfer from Chase to Aeroplan or United, Amex to ANA, Avianca or Aeroplan, or Citi, Brex, or Capital One to Avianca as well.