Chicago: United Airlines plans to ground dozens of its least fuel-efficient aircraft in an effort to conserve cash and cope with spiraling fuel prices, according to published reports.

The Chicago Tribune reported Tuesday night that United escalated the plan in mid-May as the Chicago-based airline cooled to a potential combination with US Airways. The report, citing unidentified sources familiar with the plans, said United would announce the decision today.

The Wall Street Journal, citing unnamed people familiar with the situation, reported that the plan will lead to a large but undetermined number of furloughs of union workers and a major reduction of routes.

United spokeswoman Jean Medina declined to comment to The Associated Press late Tuesday.

UAL Corp.’s United and US Airways Group Inc. told employees last week that they did not plan to combine “for now” after the companies had spent months exploring a deal that would have enabled them to shed costs.

United intends to retire 94 decades-old Boeing 737 jets, the Tribune reported. The airline had already planned to ground 30 737-500s, but the latest decision will phase out 64 more 737-300s. United’s mainline fleet includes 460 aircraft, with commuter affiliates operating hundreds of smaller planes.

United also plans to ground some of its largest jets, Boeing 747s, that are mostly used for flights to Asia and Australia, the Tribune said.

The cuts will take place through the end of 2009.

The Journal reported United will announce more reductions of salaried and management workers. That’s in addition to the approximately 500 jobs the airline recently said it would cut. Union jobs were expected to be cut later, the sources said.

The Journal also said United will eliminate its coach-only “Ted” service for domestic destinations and add first-class cabins on some of those planes.