Date: 201507
Local time of day: 1201-1800
Location: DEN.Airport, CO
Flight conditions: VMC
Weather elements / visibility: Thunderstorm
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 ZDV
ATC / advisory: Center ZDV
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Weather
Primary problem: Weather

Narrative: Flight to DEN was the last leg of a busy three-day trip with the day scheduled for 8:28 block flight time with the final leg scheduled for 2:35 flight time. I was the Pilot Flying and we departed on time with the legal amount of time left in our day to complete the flight to DEN; adequate fuel for the route filed; and a very full aircraft. Denver was forecast for the typical PM thunderstorm activity and we had an alternate of ABQ and COS. [Shortly after takeoff] we were cleared direct to LKT with rest of routing unchanged. After LKT; we were assigned a new arrival; the ANCHR 3; into DEN due to thunderstorms. We could deduce by ATC and other airlines that Denver arrivals were really being affected by thunderstorms and things were stacking up. Upon passing BFF; we were vectored off the arrival and given a southerly heading by a Controller who was highly saturated. Then we were turned back north nearly on top of Sidney; NE told to hold there with an EFC [25 minutes in the future]. At this point in time; we realized that we were not going to land in Denver for possibly another hour and that became concerning. Because of the highly saturated ATC; it was very difficult to communicate in a timely fashion. Our work load increased exponentially within a matter of minutes: navigating the aircraft; communicating with ATC; trying to coordinate Dispatch over ACARS; keeping the F/A's and Passengers in the loop; as well as communicating with each other. Our fuel quantity was starting to concern us and we had to continually stop and get back into the green RRM. I was tired and feeling a bit concerned about fuel; WX; exceeding duty time; and the possibility of landing at an off station airport. We told the Controller that we needed to receive the most direct routing back to DEN or our fuel could be an issue. They cleared us direct LAR (Laramie) for the FRNCH 3 Arrival. Along the way; the Captain and I discussed our alternate plan and we decided it would be Cheyenne; WY; which would be suitable for WX and technically for the 737. Flying all the way to LAR would have used quite a bit more fuel and as we flew past the edge of the thunderstorm; I asked the Captain to get me direct to a point on the arrival; they gave us SKARF and cleared us to fly the arrival. We landed safely and taxied to the gate. I think that as a Flight Crew we were lulled into complacency by several factors: fatigue; nice WX during the first two legs of the day; poor advanced warning about rapid deteriorating WX in Denver both by ATC and Dispatch. This caused us to fly away from our destination with our fuel decreasing and our legal flight time timing out; thus limiting our options. In hind sight; I want to be a bit more proactive in communicating and monitoring the developments. When we were assigned direct BFF that should have been our cue to contact Dispatch about the possibility of heading to our alternate. But complacency can creep up on a Flight Crew and I was starting to feel the effects of a long trip which accentuates these things. I realize that both ATC and Dispatch become task saturated during events like this; however; communicating by ACARS is slow and we need real time WX and communication because it loads up the Pilots when we cannot get quicker real time information.




Synopsis: B737 First Officer describes a difficult arrival to DEN due to weather; holding; and fuel considerations.