A Republic Airlines jetliner carrying 86 people from Fresno to Phoenix Saturday morning temporarily lost one of its two engines, then made a safe emergency landing at an Air Force base after the crew discovered the plane was almost out of fuel.

National Transportation Safety Board officials, investigating the incident, said yesterday that Republic Flight 366 left Fresno without refueling and that the crew apparently did not discover a fuel shortage until a warning light came on and an engine shut down.

A fuel gauge check, including a test to determine if the gauge is working properly, is a required part of the crew's pre-takeoff checklist, according to both federal sources and Republic.

The plane, a McDonnell Douglas DC9-30, was about 60 miles out of Phoenix' Sky Harbor at an altitude of 24,000 feet. The crew was able to restart the engine and land under full power at Luke Air Force Base, 20 miles closer than Sky Harbor. A check showed a total of 4 5/8 gallons of usable fuel remaining in the three tanks, investigators said.

"Obviously, there are a lot of questions here," safety board spokesman Bob Buckhorn said.

It was the second time in recent weeks that a Republic crew has had fuel problems. On April 2, a Republic flight carry 145 people from Minneapolis to Los Angeles lost power in both engines. The plane glided from 33,000 feet to 12,000 feet close to the mountainous peaks north of Bryce Canyon, Utah, before the engines were restarted.

In that case, investigators discovered that crew members had failed to switch to a filled fuel tank. Republic, in an official statement at that time, said its initial investigation indicated "the prescribed checklist was not followed in the initial stages of flight."

Saturday's incident began on Friday, when the same crew and the same plane flew from Phoenix to Fresno. About 15,000 pounds of fuel (2,143 gallons) were taken aboard at Phoenix. Saturday morning, when the crew prepared to fly back to Phoenix, the Fresno agent told the captain no fuel had been added and the plane had 15,000 pounds on board, according to safety board officials.

They also said that the plane had apparently used 8,000 pounds of fuel in the Friday flight from Phoenix to Fresno, so would have had only 7,000 pounds left for the return.

Crew members were identified by the safety board as pilot J. Stergiou and copilot Steve Henry. A Republic spokesman said both crewmembers had been suspended pending outcome of the investigation.