It is not TACA (IATA: TA), it is LACSA (IATA: LR) the airline that has the 5th freedom rights on the MEX-LAX route... (although they both are part of the Grupo TACA alliance) they suspended the route for some time due to bad load factor and increased competition, and they were going to loose the 5th freedom rights because Avianca wanted the route, so they decided to re-start the flight for the holiday season, which is a strong one. They re-started in november, but don't know the exact day. The only problem is that they still fly with the same horrible times:
LR690 MEX-LAX 9:25pm - 11:15pm
LR691 LAX-MEX 12.:30am - 6:10am
although I flew Mexicana on the 12:00am flight two months ago and it was packed... I wonder why Lacsa can't get enough passenger.