Island hopping in Hawaii just took a mileage jump for Mileage Plus members. Booking an interisland award flight with United for travel on partner Island Air will now require 50 percent more miles. Prior to the increase, members could redeem 5,000 miles for a roundtrip interisland award–the current cost of a one-way award. To book a roundtrip award flight, you will now need to redeem 10,000 miles.