Date: 201605
Local time of day: 0001-0600
Location: ZZZZ.ARTCC, FO
Flight conditions: VMC
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZZ
ATC / advisory: Center ZZZZ
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural FAR; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Aircraft; MEL
Primary problem: MEL

Narrative: We came across a very unusual circumstance that put the pilots in a tight spot. Both the First Officer and I deadheaded to fly the same aircraft back to the originating airport. During taxi-in we heard a strange noise from the over wing. While at the gate and after clearing Customs we had a pack trip off. After two resets; it was evident the PACK was broken. By this time the aircraft was fully boarded. After a lengthy discussion with Maintenance MX and Dispatch we concluded that the PACK would be MELed and we would return. The difficult part of the decision came due to the fact that extended overwater operations required a minimum altitude of FL 250 and the maximum altitude of the MEL was FL250. Flying west required an even altitude like FL 240. If we fly at any altitude less than FL250 we would have to hug the coast and make a fuel stop on an international flight with Flight Duty Period (FDP) for the Pilots coming into limits.Along the coastline there was a large line of thunderstorms complicating the route. Dispatch was able to contact ATC and pre-approve us for FL250 wrong direction. The First Officer and I discussed that if for any reason like ATC or weather that required us to change altitude over the middle of the Gulf; we would climb knowing the single pack operation could support a higher altitude.Once we checked-on with ATC Center and more than 100 NM from land; he demanded that we fly at an even altitude. We argued for a few minutes; but he was not giving in. We climbed to FL 260 and alerted Dispatch. Dispatch made some phone calls; and ATC Center cleared us back down to FL250 just two minutes later. We continued at FL250 until we were over land then descended to FL 240 and landed without incident.This was a situation that had very few options that everything needed to be perfect in order to be legal. Flying at FL 240 or FL 260 would have made us illegal but never unsafe. As a Crew we were comfortable with the decision; but it was unfortunate we had to make a decision to that would put us in violation of a regulation or procedure.




Synopsis: During flight in a B737-700 the crew climbed to FL260 when they were restricted to FL250 due to a single pack operation.