Air China gets a lot of flack on here, but I've done 4 flights with them and had no problems - comfortable, interesting experience, different food.
And at the end of it you're in Barajas Airport in Madrid, heart of Spain!
Dates: various from Feb-August 2019 (if you stay in July you could go to Running of the Bulls, La Tomatina in late August)
Airline: Air China
Alliance: Star Alliance
"Interesting experience"
Ok….