B737 flight crew reported hearing a loud banging noise and the First Officer saw an object hit the aircraft in cruise flight. Flight crew continued to destination and landed.
Synopsis
B737 flight crew reported hearing a loud banging noise and the First Officer saw an object hit the aircraft in cruise flight. Flight crew continued to destination and landed.
Narrative
We were operating FLT XXXX cruising at FL350 in VMC conditions smooth air. All of a sudden; we heard a loud; single banging noise that sounded like a bird strike or something hitting the airplane. The noise came from the right side of the aircraft around and just below the First Officers window. I heard the noise but did not see an object as I was looking elsewhere at the time. The First Officer stated that he saw something hit the aircraft out of the corner of his eye and it appeared to be white. We also had a jumpseater who heard the noise but did not see it. We reported the event to ATC. They had no traffic right around us and we never got a TCAS TA or RA. They gave us a number to call when we landed for more information. I called the number after landing and they just wanted to make sure we were ok. All airplane systems were normal after the incident including pressurization; engines and hydraulics. There was also no cracks in any of the windshields. We pressed on and I messaged Dispatch to set up a conference call with them; Maintenance Control; and the Chief Pilot. All parties agreed to continue the flight to ZZZ. No emergency was declared. After landing; I wrote the airplane up in the maintenance logbook. Maintenance met the plane and they had 3 to 4 mechanics do a visual inspection. My FO and I also did an exterior inspection. No damage whatsoever was found on the airplane. I then went inside the Flight Office and called dispatch and verbally debriefed with them over the phone per the FOM and then called ATC.I can't imagine what this might have been at FL350. No bird or drone I know of can get that high. ATC thought it could have possibly been a broken off piece of a weather balloon. We thought as much outside the box as possible. I thought maybe it could have been the FO's window not seated properly and all of a sudden; the pressure jammed it in place. But there was no squealing and we were pressurized just fine for over an hour. We also checked our water bottles to see if maybe pressure on them caused them to collapse or expand. Mine had never been opened and was normal. The FO's water bottle was also normal and the jumpseaters water bottle was empty and not collapsed either. I thought for sure we would land and see a huge dent in the side of the airplane but there was absolutely nothing. A possible compressor stall also ran through my mind. But we had no abnormal engine indications at all. We were in smooth air and nothing changed with power or conditions during that time. It sounded just like a bird strike to me. I'm really not sure what on earth happened up there.
Second reporter narrative
At cruise; with the autopilot engaged we hit an unknown object. I happen to be watching outside and saw the object a moment before it hit; without any time to react. We advised ATC about the occurrence. We couldn't find an QRC/QRH procedures to run. We conferenced with Maintenance Control; Dispatch and the Chief Pilot. We also asked the Flight Attendants if they saw or heard any damage to the airframe; thinking it could have struck the tail or wing.No damage was noted; in flight or after. No abnormal engine; flight control or flight instruments indications were noted at any time.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.