Narrative:

During cruise I noticed the right engine was indicating lower thrust than the left. It had been a very smooth reduction with no apparent noise change. The engine pressure ratio (EPR) was high relative to the left engine and the other engine indications were low. Though we were above the clouds; I turned on engine anti ice because of the disparate EPR / N1 indications. This resulted in no change. Pushing the throttle forward would yield only 3;000 pounds per hour (pph) fuel flow. The airspeed began to bleed off at this point and the rudder/aileron displacement was commensurate with a lower thrust on the right side.we contacted dispatch; [maintenance]; [operations manager]; and got a lower altitude from ATC. There was no EICAS message except for a 'datalink lost.' I was assuming a fuel control problem and didn't know if it was going to further degrade the thrust; so was hesitant to continue toward the high terrain ahead and opted for a diversion to [a nearby airport]. We coordinated this with the above authorities and proceeded to [alternate]. About 20 minutes from [alternate]; the right engine regained normal function and stayed that way through the landing and taxi in.in flight; [maintenance] was showing normal indications from the aircraft (though we had an EICAS message of no datalink) and the mechanic said the data he pulled up showed no abnormalities. We emailed photos of our engine indications to [maintenance] and they are sending mechanics tomorrow to look into it.

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Original NASA ASRS Text

Title: B757 flight crew reported experiencing a power loss in the right engine at cruise altitude. Flight diverted to a nearby alternate; and the engine began operating normally during the descent.

Narrative: During cruise I noticed the right engine was indicating lower thrust than the left. It had been a very smooth reduction with no apparent noise change. The Engine Pressure Ratio (EPR) was high relative to the left engine and the other engine indications were low. Though we were above the clouds; I turned on engine anti ice because of the disparate EPR / N1 indications. This resulted in no change. Pushing the throttle forward would yield only 3;000 Pounds Per Hour (PPH) fuel flow. The airspeed began to bleed off at this point and the rudder/aileron displacement was commensurate with a lower thrust on the right side.We contacted dispatch; [maintenance]; [Operations Manager]; and got a lower altitude from ATC. There was no EICAS message except for a 'datalink lost.' I was assuming a fuel control problem and didn't know if it was going to further degrade the thrust; so was hesitant to continue toward the high terrain ahead and opted for a diversion to [a nearby airport]. We coordinated this with the above authorities and proceeded to [alternate]. About 20 minutes from [alternate]; the right engine regained normal function and stayed that way through the landing and taxi in.In flight; [maintenance] was showing normal indications from the aircraft (though we had an EICAS message of no datalink) and the mechanic said the data he pulled up showed no abnormalities. We emailed photos of our engine indications to [maintenance] and they are sending mechanics tomorrow to look into it.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.