Date: 201709
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Other / Unknown
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown; Ground Event / Encounter Person / Animal / Bird
Detector: Person Other Person
When detected: Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed
Contributing factors: Company Policy; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: Airport customs requires that aircraft departing for an international destination have a pre-departure inspection. The crew is not allowed on the aircraft during the inspection. While waiting at the gate for the inspection to be completed; the gate agent came out of the gateway followed by several people in business dress. Well within hearing distance of the passengers; the gate agent said Captain I am required to inform you that while cleaning the cockpit; the cleaning crew saw a snake under the captain's pedals. The snake got away and they have not been able to find it. I am required to tell you this.At this time; the inspection was complete and I was allowed on the aircraft. I found two mechanics in the flight deck. I was informed that they had not been able to find the snake and they were not able to say with certainty what species of snake it was. The logbook had not been notated with a write up. I placed a write up in the book. I was also getting a line check on this flight. The check airman told me that his father was deathly afraid of snakes and suggested that some passengers on the flight may suffer with the same conditions.I contacted dispatch and discussed with them that I was uncomfortable taking the aircraft with an unknown reptile condition. The dispatcher agreed there was an unknown condition in the aircraft and the possibility that a snake could expose itself in flight or worse on the approach come out from under the rudder pedals. Dispatch agreed with my position. The gate agent then asked to board the aircraft. I said no; as we might be changing aircraft. I then contacted the Chief Pilot. I explained the situation and told him I was uncomfortable flying the aircraft without determining what the condition of the snake was. I had specifically asked if the cleaning crew had really had seen a snake? I was informed yes; that they had tried to vacuum it up and it had slithered away. The Chief Pilot agreed with me and told me he would have a new aircraft for us in five minutes. We were assigned the aircraft at the gate next door.The aircraft had to go through an international departure inspection. It took about forty-five minutes to get the inspection done. During that time; the tower called twice. There were no gate agents so I answered the phone. The first time the agent said; 'We got you a new aircraft are you going to board?' I said we were standing around twiddling our thumbs waiting for an international departure inspection. The second inspection was a different person who identified himself as a manager. He had the same aggressive attitude and asked if we were going to board. I replied the same response. He hung up the phone. The inspection was finally completed; we boarded and departed one hour late.During this process; I felt pressured by the tower personnel to board and take an aircraft in an unknown safety condition. I also felt that if I had not placed the write-up I the book the tower would have tried to ignore the condition of the aircraft and the possible safety issue if a snake had exposed itself in flight. Unconfirmed when I returned; I asked a gate agent what had happened to the 'snake airplane'. I was told the aircraft was left in service and the next Captain had been asked to sign some type of form stating he was informed the snake had not been found.




Synopsis: Air Carrier Captain reported that a cleaning crew saw a snake under the Captain's rudder pedals and was unable to capture it. The aircraft was rejected.