This is an example of Hidden City flight arbitrage. One particular carrier Avianca has a code-share agreement with EVA Air for flights to Taipei, China. This allows you collect miles and save money!
If you are based in the United States... You can route both ways via LAX/SFO or JFK.... SAL-LAX-TPE is $2,352 versus $4927 for LAX-TPE...
You need to collect your luggage on the return layover that makes it easy to miss the last segment... 😏
The flight ex-SAL leaves 3:20 PM so lot's of opportunities for in-bound flights... See some fun options of things to do in less than 4 hours in San Salvador!
What to do in San Salvador?
If you decide to use this ticket and have a long connection in San Salvador, the Joya de Cerén archaeological site which is sometimes called the Pompeii of the Americas is a short taxi ride from the airport. 4 hour tours from the airport can be arranged for under 100 USD depending on your level of Spanish. Joya de Ceren was named a UNESCO World Heritage Site in 1993.
EVA Air Boeing 777 Business Class
Avianca Airbus 320 Business Class