Narrative:

Established in level cruise flight at FL380 there was a loud rumble from the left engine and subsequent loss of thrust. This was accompanied by an aircraft yaw and slight vibration. I called for the driftdown checklist and commenced descent. Left throttle was reduced to idle to alleviate engine noise/slight vibration. ATC [was advised]. Attempted contact with dispatch/maintenance via ACARS. Dispatch responded with a [commercial radio] freq. Comms with dispatch on [commercial radio] VHF frequency kept getting interrupted/cut off by more mundane message traffic. This was getting to be a source of frustration and time consumption so the decision was made to abandon further attempts to communicate with dispatch/maintenance. The decision was made to divert to the nearest suitable airport; in point of time; where a safe landing could be made. Dispatch was notified of the diversion via ACARS. Flight attendant's were briefed. Pax were briefed by captain over PA. A transfer of aircraft control was conducted due to the captain's extensive experience on the airplane. The [single engine] approach and landing checklist was accomplished followed by an uneventful landing with crash fire rescue equipment notified and standing by along runway. We exited the runway and stopped the jet on a taxiway; shut down the left engine and requested crash fire rescue equipment personnel to inspect the airplane with an emphasis on the left engine. They informed us on ground control frequency that the jet looked ok and no fire; smoke; fluids or damage was visible on left engine. We elected to taxi to the gate for a routine passenger deplaning.

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Original NASA ASRS Text

Title: B737 First Officer reported diverting to a nearby alternate after experiencing a loss of thrust on the left engine at FL380.

Narrative: Established in level cruise flight at FL380 there was a loud rumble from the left engine and subsequent loss of thrust. This was accompanied by an aircraft yaw and slight vibration. I called for the driftdown checklist and commenced descent. Left throttle was reduced to idle to alleviate engine noise/slight vibration. ATC [was advised]. Attempted contact with Dispatch/Maintenance via ACARS. Dispatch responded with a [Commercial Radio] freq. Comms with dispatch on [Commercial Radio] VHF frequency kept getting interrupted/cut off by more mundane message traffic. This was getting to be a source of frustration and time consumption so the decision was made to abandon further attempts to communicate with Dispatch/Maintenance. The decision was made to divert to the nearest suitable airport; in point of time; where a safe landing could be made. Dispatch was notified of the diversion via ACARS. FA's were briefed. Pax were briefed by Captain over PA. A transfer of aircraft control was conducted due to the Captain's extensive experience on the airplane. The [single engine] approach and landing checklist was accomplished followed by an uneventful landing with CFR notified and standing by along runway. We exited the runway and stopped the jet on a taxiway; shut down the left engine and requested CFR personnel to inspect the airplane with an emphasis on the left engine. They informed us on ground control frequency that the jet looked OK and no fire; smoke; fluids or damage was visible on left engine. We elected to taxi to the gate for a routine passenger deplaning.

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.