Date: 202007
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Night
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Fire/Overheat Warning
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: This was leg 1 of day 1 of our work week of flying. The flight had followed normal procedures; practices; and expectations from preflight through initial climb. I was pilot flying on this leg and the Captain was pilot monitoring. We were communicating with ZZZ center and given our final climb clearance to filed cruise altitude of FL360. Climbing through approximately FL250 we received an aural alert accompanied by the master warning and both FWD CARGO FIRE and AFT CARGO FIRE Eicas messages. We both acknowledged the warning and tried to assess the gravity of the situation. There was enough time for me to glance at the center console and see the FWD and AFT Cargo fire lights illuminated there as well and then the aural warning went away followed by the visual warnings. We had not accomplished any actionable QRH items at this point and at this point we had to reassess and the Captain offered that we don't know for sure why the warnings started or ended but we were closer to ZZZ and this is an issue better sorted out on the ground to which I agreed. We were passing through approximately FL280 when the Captain advised ATC and requested a return to ZZZ. The Controller was quick acting and gave us a right turn and descend to FL230 I think. We eventually received further clearance to descend to 2;000 and join the ILS XXR approach from the ZZZZZ intersection with the Captain still in the pilot monitoring role. The approach controller offered Runway XXC but we both concluded that landing on Ruwnay XXR was still prudent and safe. We descended in FLCH at some speed close to the zipper for most of the descent; we confirmed flight above 250 kts below 10;000 feet with ATC; we started configuring and the Captain and I switched pilot roles somewhere outside of ZZZZZ. The switch wasn't pre briefed but seemed organic to the situation with landing weight and all other factors and so I continued as pilot monitoring from that point. We landed Runway XXR and exited taxiway X and the only issue we encountered was communicating with the fire rescue on frequency. We could communicate with Tower effectively however; we could hear rescue talk but they could not seem to hear our response. This was from both the Captain and my side of the radios. The rest of the taxi in was uneventful.We are not aware of the cause; we just responded to fire warnings and thought returning and sorting it out on the ground was safer than sorry.


Second narrative: I was the Pilot Monitoring and the First Officer was the Pilot Flying. We were passing FL250 in the climb when we received a FWD and AFT CARGO FIRE EICAS alert as well as the aural tone. I turned on the overhead light to increase crew awareness. As we were about to initiate the QRH (approximately 5-10 seconds) both EICAS alerts cleared. I stayed acting as PM while we coordinated a return to ZZZ and my First Officer stayed as the Pilot Flying. We leveled at approximately FL280 and initiated a speed increase and a turn towards ZZZ; we elected to not discharge fire bottles due to the indications clearing themselves and wanting to have firefighting capabilities in the event the light came back on. The First Officer and I concurred that a precautionary return to ZZZ was appropriate despite not having any further indications of fire. Upon requesting priority handling with Center; we were cleared direct ZZZ with a descent to FL230. Approaching FL230 we were cleared direct ZZZZZ (IAF) and a descent to 3;000 feet with high speed below 10;000 feet authorized. Approach control offered Runway XXC for landing (for the longer runway); but the First Officer and I concurred that Runway XXR was sufficient and was already thoroughly briefed. At approximately 10 miles from the field at 3;000 feet; I took control of the airplane and the First Officer became the Pilot Monitoring. An uneventful landing on Runway XXR ensued. Upon rollout we cleared the runway and came to a stop on Taxiway X. Ground Control transferred us to CFR (Crash fire rescue) frequency. CFR had difficulty contacting us; therefore Ground Control had to relay all comms. CFR did a temperature scan of the fuselage and determined we were likely NOT on fire. First Officer and I discussed and elected to return to gate. We taxied to gate uneventfully.


Synopsis: B757 flight crew performed an air turnback after receiving Fire Warning indication for both cargo compartments.