Some recent Boston championship banners adorn the renovated JetBlue terminal at Logan Airport. JetBlue, which has more flights out of Boston’s Logan Airport than any other carrier, unveiled phase one of its $50 million Terminal C upgrades on Monday, including new kiosks and ticket counters. Twenty-five kiosks and 30 check-in counters are in use in what is called the North Pod, where United Airlines check-in counters used to be located.