Hello. Aeromexico has a very strict progression. You begin at their regional as a SAAB 340 or ERJ-145 FO (or CAP if you have more than 3,000 hrs). From there you would go as an FO to Aeromexico, most likely the B737 or MDs. You would remain as an FO in progressively larger planes (B767-777), then return as Captain to the B737 or MD and work your way up as Captain. This of course takes a lifetime. There are no cuts, you have to wait for your turn, and I don't know if it's a rumor but I've heard there are pilots who reitre as FOs.
Mexicana is the same.
One more thing, you must become a member of ASPA first. The airline hires only through them. It's kind of complex.
Check out Volaris. They fly A319 out of Toluca and have direct entry Captain positions. There are several other airlines where you could start as a Captain, AMX and MXA have very strict rules and most people in there do their whole careers there and start at an early age. PM me if you want.