An airline can zero out inventory in any fare they don't want to sell, for example
If they accidentally posted the wrong fare (e.g. $90 instead of $900), they could zero out a bucket to prevent anyone from buying it.
If the airline or route are suspended (e.g. diplomatic or regulatory issues), then all seats may be zeroed out, because the route is not ...
At Mexico City Airport, if you are just connecting to an onwards destination, your baggage would be checked in for it's final destination if it's an international one. Otherwise you will have to collect it and pass through customs.
However you'll have to check if the airline has any restrictions. You can do that while booking your flight or by calling up ...
Aeromexico states at the bottom of their baggage information page that boxes or coolers are allowed as long as they are seal-wrapped.
Baggage Wrapping Services
"Secure Wrap" services can be found at select airports. This service is designed to protect your baggage for a low fee.
Boxes and Coolers
Secure Wrap is required for passengers traveling ...
Indeed, the only mention of cardboard boxes in the context of luggage that I can find on Aeroméxico's website is talking about transporting chickens on internal flights. (For internal flights, cardboard boxes are ok; for international flights, chickens have to be in wooden boxes).
Google also finds a comment on Facebook by someone who says (my translation ...
According to the summary on Wikipedia, no.
The flight operated by AeroMexico originating at MEX is exempt for not meeting this provision:
"travelling to an EU member state on an airline based in an EU member state"
AeroMexico is based in Mexico.
Please don't over complicate this. Redeeming vouchers is a common occurrence.
Most often, the easiest thing to do is make a reservation (reserve only, don't pay) on the airlines website, then call directly to redeem the vouchers.
They will tell you exactly what to do with the vouchers and take payment for any remaining balance.
You don't need an agent ...