British Airways has ticket prices for Los Angeles to Barcelona around $500 round trip in August. These tickets are reduced by up to $65 using British Airways AARP link. AARP membership is $16 and available to members with no age restriction.
British Airways AARP ticket $435.23 round trip
Los Angeles LAX – Chicago ORD – Barcelona BCN – ORD – LAX
British Airways AARP ticket $462.25 round trip
Los Angeles LAX – Dublin DUB – Rome FCO – Dallas DFW – LAX