DENVER, May 31 (Reuters) - Frontier Airlines Inc. (FRNT) said on Friday it will eliminate travel agent commissions for tickets sold in the United States and Canada, joining most U.S. carriers in cutting commissions to boost revenue. The Denver-based low cost airline said the change also applies to commissions paid on change fees and takes effect at 10:01 p.m. MDT Friday (0401 GMT). Frontier had maintained commissions even as other carriers eliminated those payments earlier in 2002, but reservations attributed to travel agents have been declining, the carrier said. ©2002 Reuters Limited.