Date: 202001
Local time of day: 1801-2400
Flight conditions: VMC
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Aircraft component: Engine
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Aircraft was at FL 360 and .78 mach when the auto throttles clicked off; we got two master warning lights; (No. 1 Engine) N1 rolled back to 45% and fluctuated. The aircraft started noticeably shaking. The First Officer was flying and pulled the number one throttle to idle; the shaking lessened but did not stop. I immediately started the APU. The flight attendants were ringing the cockpit; I had cabin now on my headset and could hear they were concerned the aircraft was shaking really bad in the back and that passengers were saying sparks and flames were coming from under the wing. I had already [advised ATC] and told them we had engine trouble. Ask them to stand by for further. I grabbed the QRC and started the ENGINE FIRE or ENGINE SERVER DAMAGE or SEPARATION check list. We did not have fire indications in the cockpit but with the shaking and reports of sparks and flames from under the wing I thought that the appropriate plan of action. I performed the checklist and First Officer flew the aircraft. We completed the first (few) steps on the QRC with in 2 minutes of the realization we had a major engine problem. After we had engine shut down I told ATC we needed lower that we had lost an engine and would get back with flight vitals. ATC told us we had ZZZ behind us we had a military base to our left and ZZZ1 straight ahead and asked out intentions. I quickly talk over with First Officer ZZZ was behind and about a thirty-minute spiral down to an unfamiliar military base; so decision was made for take straight in to ZZZ1. I completed the check list in QRH while First Officer flew and do normal radio. I coordinated with the flight attendants we had shut down the morning #1 engine we had [advised ATC] and that we were going to make a single engine landing in ZZZ1. I told them I would get back with the as far as the time to ETA and that we were not expecting an evacuation; I also told them I would make an announcement to the passengers shortly. I told ATC that we wanted the longest runway and to have safety vehicles to meet the aircraft at the runway about mid field. First Officer and I briefed the approach for Runway XX ZZZ1. We used a 1;000 fpm descent to allow descent rate with minimal power to maintain safe airspeed get the aircraft to 12;000 ft. about 20 miles from ZZZ1. I told First Officer I hope he didn't mind but I felt more comfortable landing the aircraft (this had no bearing on his ability his performance was stellar). At 12;000 ft. I took the aircraft and asked First Officer to verify all items on the check list were complete. We held off on the Grd Prox switch for the flaps 15 landing so we could keep out speed above 250 kts. Having First Officer verify items was to make sure this item and all others were complete; First Officer accomplished a non standard landing. I gave the cabin a 10 minute prep and a quick announcement for passengers before descending below 10;000 ft. Flew down wind slowing and descending to 3;000 ft. turned base at 12 miles. Completed a successful stable single engine landing on Runway XX ZZZ1. Stopped the aircraft at mid field. Told passengers remain seated three times. Safety equipment came to aircraft inspected entire aircraft were given the ok to taxi to gate. Safety equipment followed us to the gate without incident. In closing Cabin crew maintained professional calm attitude. More than effectively conveyed situation in the cabin to the flight deck so the best information was available. First Officer was stellar in his performance was level headed. He was task orientated focused and relayed information promptly and succinctly. He made sure I had all the information I needed to make decisions. This entire crew should receive recognitions for their duties preformed during this in flight emergency.


Second narrative: At FL 360 cruising to ZZZ the airplane started to shake noticeably and at the same time the auto throttle disconnected. Looking for clues the Flight Attendant called us reporting the shaking problem. The Captain and I realized the (No. 1) N1 dropped to approx. 45%; while the N2 was still around 85-90%; and a quick scan of the instruments nothing else out of the normal. The Flight Attendant called us the second time reporting passengers looking out the window saw sparking and fire below the left wing. We quickly realized we were losing the left engine. We [advised ATC] and we headed to ZZZ. We complied with the appropriate check list and descended to a lower altitude. We requested the longest runway in ZZZ (Runway XX) and the assistance from [crash fire rescue] on the ground. I flew the airplane while the Captain finished the check list and prepared the cabin crew for the emergency landing and he did the PA to the passengers. After that; the Captain flew the airplane and accomplished the landing at ZZZ on Runway XX runway. We stopped the aircraft on the runway and verified with [crash fire rescue] that the aircraft was safe to taxi to the gate.


Synopsis: B737 flight crew reported an engine failure in cruise that resulted in a single engine landing at the destination airport.