Date: 201907
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition
Contributing factors: Human Factors; Aircraft
Primary problem: Aircraft

Narrative: Just prior to the Top of Descent into ZZZ from ZZZ1; the flight attendants called to inform us of an odor described as 'burning rubber and electrical' centered around row 16. Several passengers noticed to odor as well. The flight attendants began their efforts to determine the source and we began the 'Smoke; Fire or Fumes' Checklist. A Company Pilot was in the back and after several minutes; the flight attendants and the pilot determined the odor was increasing. We [advised ATC] and were given direct to ZZZ. I then advised the passengers of the situation and that we were a [priority] aircraft. The flight attendants prepared the cabin for landing and the First Officer and I determined a diversion to ZZZ2 was not warranted. We landed on [Runway] XXL without incident. As we cleared the runway; CFR inspected the aircraft and found the left main landing gear brakes were glowing. We proceeded slowly to the gate with CFR in tow. We called Ops to inform ground personnel to avoid the aircraft until it could be determined safe to approach the aircraft.In retrospect; I should have briefed the flight attendants in the cabin for normal landing. On final we heard the commands from the cabin; which was not warranted at that time which surprised us because I had the First Officer check on the situation just prior to base leg one more time and the odor was stable. Earlier; I had informed the flight attendants an evacuation was not warranted. Although; if I had just asked them to secure the cabin and the situation escalated; we would regret not preparing the cabin. Also; a BRACE! BRACE! BRACE! command was not warranted or given over the PA; so I am not sure the 'Heads Down Stay Down' commands were correct procedure.  There was a breakdown in communication and of overall knowledge of cabin procedures on my part to have the proper game plan in place before arrival.


Second narrative: At cruise FL 390; approximately 100 miles prior to planned STAR descent; a Flight Attendant informed Captain that a 'burning rubber' smell was prevalent near row 16. Neither the Captain nor I could smell it. It was asked if there was any smoke or haze visible and we were informed there was not. The Captain decided that an [ATC should be advised]. There was a brief discussion about nearby airports of which there were plenty; but we decided to continue to ZZZ with the priority handling (Direct ZZZ; speed/ALT our discretion). The smoke/fire/fumes QRH was actioned intermittently as workload/communication permitted. We proceed direct to ZZZ at high speed (300 knots). After [advising ATC]; I did not monitor communication between Captain and cabin; as to better monitor the aircraft state and communicate with ATC. QRH was not completed because of the short time to landing and the condition in the cabin not escalating. Speed was high on downwind and a short turn to final with a flaps 40 landing. 'Heads down stay down' could be heard upon slowing and turning short final. After clearing the runway; we stopped and ARFF was asked to inspect the aircraft briefly with much communication problems and the only thing to report was a 'glowing' brake. Taxi to gate; deplane; go home. The smell in the cabin seemed to create a false sense of urgency and greater distraction than necessary. At no time was there any smoke or haze visible; nor did the smell worsen. In addition; the company pilot traveling in the back was asked if he could smell it; and he stated that he could not smell it over the fragrance/lotion that someone had put on near him. At no time could it be smelt on the flight deck or the extremities of the cabin. Communication: There was a breakdown in communication between the cockpit and cabin as to 'emergency' Relevant to ATC; yes; [ATC was advised] as a precaution; but at no time was the safety of the aircraft ever in question. The 'emergency' word was used in communicating with the cabin which resulted in a misconception of how the remainder of the flight was going to be conducted with regard to safety procedures when in reality we just needed priority handling to land with no undue delay. The false sense of peril and urgency resulted in a confused state in the cabin and an undesirable state of the aircraft which put us in a far greater state of risk than the event which precipitated the 'emergency' in the first place. The Captain continued to perform Pilot Flying duties as well as frequent communication with the cabin during a high workload phase of flight. This was further compounded by a high energy approach and resultant unstable approach.


Synopsis: B737-700 flight crew reported strong burning rubber smell throughout the aircraft resulting in an uneventful landing at destination.