I think you're wrong. They do fly to Tijuana, as a matter of fact, I passed by Tijuana International Airport about 2 weeks ago and saw a 727-200 of theirs. I did pass by the ticket counter inside the airport and I saw that they had several flights out of Tijuana. As a matter of fact, they do fly internationaly.
Aviacsa fly's to Las Vegas and Dallas from Monterrey. I just heard that they purchased or leased 6 737-200's from Air New Zealand. That means that they are getting rid of their 727's and DC-9-10s
You can visit their website @ www.aviacsa.com.mx
Have a happy new year
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