US airline United has raised some of the prices in its MileagePlus frequent-flier reward program, upping the number of miles flown to receive some benefits. As of Feb. 1, frequent-flier reward programs for trips to Europe, the Middle East, Africa and Asia will change, although most of the program for domestic flights will stay the same, the Chicago Tribune reported Saturday. One exception concerns flights to Hawaii. After Feb. 1, it will require 45,000 miles of travel to earn a round trip seat in coach to Hawaii -- up from 40,000 miles, the newspaper said. Other changes include reward trips to Europe. What currently requires 135,000 miles of travel to earn a round trip flight to Europe will require 160,000 miles, the airline said.