Date: 202010
Flight conditions: VMC
Weather elements / visibility: Thunderstorm
Aircraft: B787 Dreamliner Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Flap/Slat Control System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Approximately one hour into the flight we got an EICAS message and audio warning: Slats Drive. We followed the ECL (Electronic Checklist) and learned that we would have to land with flaps 20 and Ref 30 + 30; and that auto land was not approved. We would need a long runway into the wind. ZZZ was landing east; so I had to chat with Center to land west; and specifically on Runway XXL due to NOTAMs for higher minimums on the other runways. ZZZ and ZZZ1 were both forecasted for low ceilings and visibility. ZZZ2 wasn't much better. ZZZ4 and ZZZ5 had good weather. I contacted Dispatch via SATCOM (Satellite Communication) and told him about our situation. We discussed the situation with Maintenance Control and the possible diversions to ZZZ5; ZZZ1; ZZZ2; and ZZZ4. ZZZ1 was the preferred diversion station; however; the TAF (Terminal Aerodrome Forecast) was worse than the other stations. I had Dispatch keep us updated on our plan. As we proceeded; I spoke with the purser and gave him the briefing. He understood that no evacuation would be necessary. He briefed the other flight attendants. I went on break and had my relief pilots call me as we passed ZZZ5; with a weather update. ZZZ was holding at 2 1/2 miles and 2-300 ceiling. I told them to continue to ZZZ; and advise me if the weather deteriorated. I went back to sleep. After break I returned to the flight deck and confirmed status; and weather. We were going to attempt an ILS to XX R; take a look; miss if we had to; then hold for a while; and if we can't get in; divert to ZZZ2 or ZZZ4. I notified ATC; that we couldn't auto land; and had to have the ILS XXR. He understood. My awesome First Officer flew a wonderful ILS and we managed to land. We told the Crash Fire Rescue people that we didn't need any help and parked with no other events. I debriefed Maintenance; and the Flight Operations Representative.


Second narrative: After reaching cruise altitude we alerted to a EICAS  message (Slats Drive). We executed the appropriate checklists; and later during the flight; made a decision to continue to our destination. The final approach speed was going to be VREF 30 + 30 knots with a flaps setting of 20 for landing. With the higher approach speed and weather conditions at the destination we notified ATC to allow a request for the longest available runway without restrictive NOTAMS. An ILS approach and landing was made on Runway XXL and taxied to the gate without incident.


Synopsis: Air Carrier Flight Crew flying 787 aircraft report Slat malfunction in flight.