Iberia, Level, and other Oneworld carriers have round-trip flights from Los Angeles (LAX) to Barcelona or Madrid (BCN/MAD) for $487-$517, NONSTOP. Barcelona flights April, May, September, October, November, December, January, and February. Madrid flights October to February. 7-day minimum stay required.
Note: Barcelona flights are on LEVEL, a budget brand of Iberia. Madrid flights are on regular full-service carriers.
Click for more details and booking links Nonstop Flights: Los Angeles to Barcelona or Madrid $487-$517 r/t [dates vary, read the full blog post] – Iberia / Oneworld / Level