Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Distraction; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
ATC Equipment / Nav Facility / Buildings; Aircraft; Human Factors
In the descent and approach environment to MMMX we were assigned multiple clearances.  The environment was task saturated and complicated by the ATC language barrier.  After intercepting the SLM 340 radial inbound; flight level change was selected.  Approaching MAVEK; I noticed the GPS-L invalid message as expected from the company pages; and I turned my focus outside of the aircraft looking for the 3/1 and for PLAZA for the turn inbound to the runway.  I was also watching for the heavy traffic we were following.  Also at this time; the Captain noticed we had descended through the 12;000 feet crossing altitude at MAVEK and that we were still in FLC.  The Captain stopped the descent and engaged VNAV.  Captain had me notify ATC and we did not understand their response.  The rest of the approach and landing was normal.I was in the yellow; and do not recall that we said or cross checked 'LNAV; VNAV; VNAV PATH; set minimums' at the time we were cleared for the approach.  Multiple times different altitudes were set in the approach environment due to the complexity of the situation.  For some reason the ATC communications on this day approaching MMMX were more complex than usual.  I recall previous MMMX and other Mexico flying experiences where the Controllers make a point of speaking slower in English to English-speaking aircraft which helps tremendously with the accent; and this was not the case yesterday.  There was also a long pause before ATC responded to my transmissions; which made the task saturation seem enhanced; as I listened for responses.I will make it a point to add extra discussion on this topic to future approach briefings into complex environments.  Specifically the importance of verbalizing and cross check of 'LNAV; VNAV; VNAV PATH; Set min' when we hear we are 'cleared for the approach' from ATC and the need to query ATC that we are 'cleared for the approach' prior to the IAF.
B737-800 First Officer reported overshooting a charted altitude on arrival into MMMX. Reporter also stated they received a GPS-L invalid message.