Narrative:

We had thoroughly briefed/reviewed the cleared route of TIKEB1C STAR mavek transition to the ILS 5R approach into MMMX. Approximately 5 minutes prior to the top of descent; ATC gave us a clearance to turn left to a heading of 060 and intercept the slm 340 radial into slm for the arrival; and descend and maintain FL350. We complied with the turn and altitude clearance while also building the new course into the FMC. A few minutes later ATC then told us to instead intercept slm 360 radial inbound. I queried the controller because neither of those radials lined up with an expected STAR.ATC then said we can expect the SASUT1C arrival; but for now to intercept slm 360 inbound. We complied again with the new change. While flying inbound on the slm 360 radial; ATC cleared us to descend while complying with the arrival altitudes. We were still not on a published segment of the arrival. I queried again about these revised clearances not being part of any arrival. ATC advised us that due to traffic they needed to keep adjusting our route and airspeed. To comply; we then had to build into the FMC both DME arcs with the charted altitude and speed values for the descent clearance given. This took several minutes to build into the FMC. Soon after we had that set up; ATC then told us to turn right to a 180 heading and to intercept the san mateo 300 radial inbound and to descend to 13000'. I advised the controller that we didn't know what the identifier for san mateo was (it was not on our STAR or expected approach). I asked again; and was still not given the identifier for san mateo. I advised ATC that we were unable to comply with the clearance; and that we were being given way too many changes for our arrival. The controller did not respond to our statement; and told us to contact a different ATC frequency.in the meantime another aircraft told us the identifier for san mateo (smo) over the radio. We then built the requested intercept radial off smo after clarifying it again twice with the next ATC. This new controller confirmed our routing. Shortly after that; ATC changed our route again to: 'proceed direct mavek and cleared for the RNAV ILS 05R.' we complied with direct mavek and prepared to fly the approach after the mavek fix. Several additional lower altitudes and airspeeds were given to us by this controller (too many to accurately remember however). We were scrambling this entire time trying to keep up with all the different clearances being issued. At one point; I asked the first officer to concentrate on just flying the aircraft; while I build and rebuilt multiple times all the different clearances into the FMC as they were being issued.

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Original NASA ASRS Text

Title: B737 NG Captain reported receiving multiple confusing clearance changes on arrival into MMMX that greatly increased workload.

Narrative: We had thoroughly briefed/reviewed the cleared route of TIKEB1C STAR MAVEK transition to the ILS 5R approach into MMMX. Approximately 5 minutes prior to the top of descent; ATC gave us a clearance to turn left to a heading of 060 and intercept the SLM 340 radial into SLM for the arrival; and descend and maintain FL350. We complied with the turn and altitude clearance while also building the new course into the FMC. A few minutes later ATC then told us to instead intercept SLM 360 radial inbound. I queried the Controller because neither of those radials lined up with an expected STAR.ATC then said we can expect the SASUT1C arrival; but for now to intercept SLM 360 inbound. We complied again with the new change. While flying inbound on the SLM 360 radial; ATC cleared us to descend while complying with the arrival altitudes. We were still not on a published segment of the arrival. I queried again about these revised clearances not being part of any arrival. ATC advised us that due to traffic they needed to keep adjusting our route and airspeed. To comply; we then had to build into the FMC both DME arcs with the charted altitude and speed values for the descent clearance given. This took several minutes to build into the FMC. Soon after we had that set up; ATC then told us to turn right to a 180 heading and to intercept the San Mateo 300 radial inbound and to descend to 13000'. I advised the Controller that we didn't know what the identifier for San Mateo was (it was not on our STAR or expected approach). I asked again; and was still not given the identifier for San Mateo. I advised ATC that we were unable to comply with the clearance; and that we were being given way too many changes for our arrival. The Controller did not respond to our statement; and told us to contact a different ATC frequency.In the meantime another aircraft told us the identifier for San Mateo (SMO) over the radio. We then built the requested intercept radial off SMO after clarifying it again twice with the next ATC. This new Controller confirmed our routing. Shortly after that; ATC changed our route again to: 'proceed direct MAVEK and cleared for the RNAV ILS 05R.' We complied with direct MAVEK and prepared to fly the approach after the MAVEK fix. Several additional lower altitudes and airspeeds were given to us by this Controller (too many to accurately remember however). We were scrambling this entire time trying to keep up with all the different clearances being issued. At one point; I asked the FO to concentrate on just flying the aircraft; while I build and rebuilt multiple times all the different clearances into the FMC as they were being issued.

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.