anything in mexico...drugs?
anything that early in the morning...pilot fatigue/error?
anything that old...mx problems?
but my guess is that the instruments and electrical system may play a role here.
or, if it did get to 20,000 feet, forgeting or having pressurization problems and pilots pass out.
and yes, these are all gueses
I hate to sound like mean spirited person, but I have met quite a few experienced *corporate* pilots from Mexico that lacked basic instrument flying skills. Some of my flight school students that got corporate gigs later in Mex told me unbelievable stories of incompetence. That's when I recommended applying for their airlines from then on.
I wonder if this was a 135 charter (or equivalent). Could get interesting in court, now that we know that the carriage of persons was prohibited. Would be interesting to find out why this restriction/limitation was added.
Not saying that the crew was incompetent, but unfortunately there's that uncertainty.
What a waste of life.
PS Looking at the name of the Fed who signed this license I am pretty sure that he got this through the SAT FSDO.