Frontier Airlines to cease Denver-Boston service Friday August 9, 1:50 PM EDT BOSTON, Aug 9 (Reuters) - Low-cost carrier Frontier Airlines (FRNT) said on Friday it will stop service between Denver and Boston in the fall after five years because it has not proved profitable enough. Frontier, a Denver-based airline that has asked for federal guarantees to back a $70 million line of credit under airline stabilization legislation approved following the Sept. 11 attacks, said the twice-daily service will stop on Oct. 22. The route has not met profit forecasts and difficulties in finding economical gate space at Boston's Logan International Airport contributed to the decision to leave, Frontier said. The 17 part- and full-time customer service workers will have the option of applying for vacancies elsewhere with Frontier. Frontier has increased capacity by 16.4 percent through July from the same period last year and on Thursday announced plans to add service from Denver to Fort Myers, Florida; Oklahoma City; and Tucson, Arizona. Earlier in August, Frontier reported a loss of $2.9 million for its fiscal first quarter, citing the slow recovery of business travel and airfares following the attacks. Roger EWROPS