Date: 201807
Local time of day: 1801-2400
Location: SPIM.ARTCC, FO
Flight conditions: VMC
Aircraft: Widebody; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: Center SPIM
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Confusion; Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Airspace Violation All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure; Chart Or Publication; Company Policy; Human Factors; Airspace Structure
Primary problem: Ambiguous

Narrative: We were on the final portion of [our] flight; at 36;000 ft inbound to join the arrival to Lima. In order to sequence another aircraft ahead of us; Lima Control instructed us to slow to .77 Mach and fly heading 265. Shortly after complying; I informed Lima that we would soon need a turn back on course for a No Fly Zone ahead. (No Fly Area NFA1 for depressurization contingencies). Lima instructed us to maintain heading. I repeated my concern but Lima instructed us to switch to the next Lima frequency. I immediately checked in with the next Lima controller; stating that I needed a turn for the upcoming No Fly Area. Lima instructed to maintain heading. Since the other aircraft was now adjacent to us on the airway and a left turn might have put us in possible conflict with it; I immediately suggested to start a right turn to return to the airway. Lima responded to maintain heading 265 for 6 minutes to join another airway. Upon realizing that Lima intended to take us through the No Fly Area; we simultaneously started an immediate right turn and announced 'PAN; PAN; PAN. [We are] turning right. You are flying us into a No Fly Zone that we cannot do for our aircraft type'.  The controller then replied; 'Roger; turn right to 090'. During the turn; the controller gave us direct to a fix. Since this would have deleted altitude step downs on the arrival; I informed Lima that we wanted to proceed to a different fix to join the arrival. Lima approved this. The arrival; approach and landing were subsequently completed without further incident. Suggestions include reminding Lima Control of certain aircraft's limitations from transiting the No Fly Zones. Also; have No Fly Zones printed on the STARS to alleviate jumping from charts and apps in the iPad to cross check. Lastly; print reminder in the ops pages that No Fly Zones' boundaries can be placed in legs 2 of the FMC for HSI map display by inserting NFZ01 through NFZ08 for NFA1 and NFZ10 through NFZ15 or so for NFA2.


Second narrative: [Report narrative contains no additional information.]


Synopsis: Air Carrier flight crew reported being vectored by Lima Control into a 'No Fly Zone.'