Business Insider toured United's newest plane, the A321XLR expected to fly to Europe and beyond.Taylor Rains/Business InsiderWe toured United Airlines' new ultra-premium Airbus A321XLR at the UK's Farnborough airshow in July.The jet has doors in business class, privacy dividers in premium economy, and a snack bar in coach.It's refreshing to see an airline add premium perks to the economy section.United Airlines' newest Airbus jet is easily the a…