Date: 201704
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: IMC
Light: Daylight
Aircraft: EMB ERJ 145 ER/LR
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 Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Training / Qualification; Situational Awareness; Workload
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Diverted
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: While cruising at FL250 the flight deck crew as well the passengers and the FA in the cabin noticed a strong burning odor. No smoke was present. The flight crew immediately donned O2 masks and [advised] ATC. ZZZ was the nearest suitable airport and a decision was made to divert there. CFR met the aircraft upon landing and did an exterior inspection of the aircraft; no evidence of fire or smoke was visible to them. Aircraft then proceeded to the gate and was deplaned. Maintenance arrived to investigate the cause.


Second narrative: Cruising at FL250 at 300 kts. We entered an area of IMC at cruise; Radar did not show any precipitation in the area but we encountered light precipitation. After about 1 minute; the comms started getting scratchy. The radar also started to show precip in all directions. I associated this with the comms getting scratchy and suspected the aircraft wasn't dissipating the static electricity well. I started to notice an odor. I couldn't put my finger on the type of smell. It had a slight electrical smell but wasn't as pungent. I made a comment to the CA and he confirmed that he smelled it as well. The CA called the FA and she confirmed that she smelled it and a passenger had just asked her about the smell. I suggested putting on O2 as a precaution; so we Donned masks. The CA called ATC and requested a diversion to ZZZ. They issued a heading and descent to 18000. The CA further communicated with the FA about looking for a source of the odor/smoke. Then messaged dispatch and talked to the passengers that we were going to ZZZ. We received a clearance to go direct to ZZZ and further descent instructions and prepared for an ILS. As we departed the area of precipitation; the odor started to dissipate. I could still smell it at 18000. By the time we descended to 4000; the smell was completely gone. We communicated our intentions with ATC that we would clear the runway and that we did not see a reason to evacuate but requested CFR to walk around the aircraft as a precaution. The landing was uneventful. We cleared the runway and contacted the Fire Supervisor and coordinated a walk around with a heat gun and found no unusual heat signatures. The taxi to gate was uneventful except our FOM page for ZZZ had an incorrect ops frequency. When we confirmed that we all smelled an odor. I suggested O2 masks as a precaution. We donned masks one at a time and confirmed communications. He [advised] ATC and as requested ZZZ and a lower altitude. We were given a heading and 18000. I asked the CA if we should do gear down and treat this as a rapid descent. He said no; so I used normal procedures in the descent. The CA was communicating with the FA and the smell seemed to be dissipating. The CA sent a message to company. I asked to run the QRH but couldn't name a specific procedure. Since the odor was dissipating it wasn't clear which procedure would be best. We definitely didn't have smoke confirmed from an electrical source but it seemed like an electrical type odor. The QRH procedure for both air conditioning smoke and electrical system fire or smoke seemed like they could make matters worse since the odor was dissipating. Time was also an issue since we needed to prepare for arrival. We received ATIS; reprogrammed the FMS and got landing numbers . I didn't want to delay arrival to run procedures since the situation seemed under control.There was confusion regarding the reprogramming of the FMS. I used the Direct button to go direct to ZZZ but since it wasn't in the flight plan; it only gave us options for our destination airport's approaches. I added ZZZ to the end of the flight plan and deleted the arrival and approach into ZZZ1. Then the FMS allowed selection of the appropriate runway and ILS. This was a distraction during a high workload situation. More training on Diversions in the FMS would be helpful. This is not a commonly used procedure and the rustiness showed.


Synopsis: EMB-145 flight crew reported they noticed a strong burning odor in the cabin and elected to divert. The odor dissipated during descent.