Date: 201501
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 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
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion
Second reporter function: First Officer; Pilot Flying
Anomaly: Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed As Precaution; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: In cruise flight; the Flight Attendants notified the Captain of an odor that was present in the cabin and seemed to be getting stronger.  The Captain and First Officer (FO) did not smell anything unusual in the cockpit.  The Flight Attendants did not see any smoke and there was no presence of fire.  The Captain then had a Flight Attendant come to the flight deck and the Captain then stood in the forward galley to smell the air. While standing in the forward galley; the Captain asked if any discolored panels or hot spots were detected in the cabin.  No discolored panels or hot spots were detected.  The presence of an unusual smell was detected by the Captain.  The smell could best be described as the smell of hot linen; the strong smell of a hot garment when an iron is immediately removed.  This smell was not the same as the usual smells in the airplane; such as a hot duct; an oily smell or even the occasional dirty sock smell in some aircraft.  The air did not seem to irritate the eyes.  The presence of the strange odor; which had increased during the flight; was enough to take the precaution of diverting the flight.  The Captain returned to the flight deck and the Flight Attendant returned to the cabin.  The Flight Crew decided to divert and Dispatch was notified via ACARS.  Center was then advised of the diversion and an emergency was declared.  Procedures for smoke/fire/fumes on the aircraft in the QRH were followed.  The Passengers were notified by PA that the diversion was taking place. The Flight Attendants were told that we were going to land; clear the runway; and be checked out by the fire department before proceeding to the gate.  We were not in an evacuation situation at that time.  Operations was notified of the diversion and that we would need a gate upon arrival and to notify Maintenance that the brake temperatures would need to be checked due to an overweight landing.  A descent and visual approach was flown by the FO until control of the aircraft was taken by the Captain at approximately 1500 feet AGL.  After exiting the runway; the fire department inspected the aircraft and gave the all clear.  The Passengers were told by the Captain and the Flight Attendants to remain seated until arriving at the gate. Write-ups for an odor in the aircraft and an overweight landing were entered into the logbook.This is a dynamic event in that significant communication between ATC; Dispatch; Flight Attendants; and Pilots (within the cockpit) and Base Operations must be accomplished with oxygen masks and eyeglasses (in this event) on.  Communication is a real barrier and must be disciplined; especially when using intercom/hot MIC. The event described above really can't be prevented from an Aircrew point of view and must be handled in accordance with the QRH and best judgment.


Second narrative: After uneventful climb and level off at FL340; a Flight Attendant (FA) called and said there was a strong smell of something hot or burning in the Passenger compartment. Up front we had no smells or smoke. Captain went back for quick look. On return; he decided to divert and run the Smoke/Fumes Checklist. On oxygen; we ran the checklist and declared an emergency with ATC. I continued to fly until final while the Captain coordinated with; ATC; the FAs; and Ops for the diversion. After running the Descent and Before Landing Checklists; Captain took the aircraft for the uneventful overweight landing. Firemen checked the outside of aircraft and found nothing. We then continued to the gate without further incident.


Synopsis: B737 Captain is informed of an odd smell in the cabin by a Flight Attendant. Odor cannot be identified nor its source located. The crew elects to divert to a suitable airport after declaring an emergency.