Narrative:

During cruise; I briefed the assigned arrival and approach and verified all restrictions associated with each. At the top of descent; we were reassigned a new arrival. We could have been cleared to descend via this new arrival at this point but neither of us remember that being the case. Upon inserting the new arrival and knowing we were now past our top of descent; we inquired as to whether or not we were cleared to descend. At this point we did receive our clearance. We were in and out of VNAV as required and even dropped the gear to ensure crossing restrictions would be met. Even so; we failed to notice and address the route discontinuity created by the insertion of the new arrival. Later; we knew we needed an approach clearance and due to frequency congestion were not able to receive one in a timely manner. Finally; we received an approach clearance and set the lower altitude in the window. At this time we were now addressing the route discontinuity and as we were verifying that everything looked ok; we descended below the published altitude; but not before we received notice that our GPS was being jammed; first one side; and then the other. I told this story to another captain and he told me that he had the same experience of receiving a new arrival at top of descent. This must stop! Mexico city is a difficult arrival and approach and requires careful and deliberate attention to detail. We feel we did our due diligence in this matter and all of that was negated by a different arrival being assigned to us beyond a reasonable point in our flight.

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Original NASA ASRS Text

Title: Air carrier Captain reported being issued a new arrival into MMMX at top of descent point without being issued a descent clearance. During descent GPS jamming and a route discontinuity were detected. A crossing restriction was overshot.

Narrative: During cruise; I briefed the assigned arrival and approach and verified all restrictions associated with each. At the top of descent; we were reassigned a new arrival. We could have been cleared to descend via this new arrival at this point but neither of us remember that being the case. Upon inserting the new arrival and knowing we were now past our top of descent; we inquired as to whether or not we were cleared to descend. At this point we did receive our clearance. We were in and out of VNAV as required and even dropped the gear to ensure crossing restrictions would be met. Even so; we failed to notice and address the route discontinuity created by the insertion of the new arrival. Later; we knew we needed an approach clearance and due to frequency congestion were not able to receive one in a timely manner. Finally; we received an approach clearance and set the lower altitude in the window. At this time we were now addressing the route discontinuity and as we were verifying that everything looked OK; we descended below the published altitude; but not before we received notice that our GPS was being jammed; first one side; and then the other. I told this story to another Captain and he told me that he had the same experience of receiving a new arrival at top of descent. THIS MUST STOP! Mexico City is a difficult arrival and approach and requires careful and deliberate attention to detail. We feel we did our due diligence in this matter and all of that was negated by a different arrival being assigned to us beyond a reasonable point in our flight.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.