Air France is offering the planes because they have them on the ground. Currently, they don´t need them. My guess would be over capacity as well.
In addition, I´d like to comment that AeroMexico´s long-haul fleet is not really that old. The 767s were adquired in the early '90s, right after the retirement of the DC-10s. The newest 763 was delivered in late '98.
After the 73G incorporation in '03, the fleet will have an average age of 7 years.
En Mexicana cumplimos 85 años de hacerte sentir el placer de volar sin limites