British Airways has Los Angeles to Rome, Paris, Barcelona and Amsterdam priced under $600 round trip. These ticket prices drop close to $500 using Momondo.com searches for online travel agency tickets or British Airways AARP discount link.
LAX to Rome and Paris discounted tickets are available for travel from mid-October to May 1, 2018.
British Airways/Aer Lingus $521.32 round trip (AARP discount)
Los Angeles LAX – London LHR – Rome FCO – Dublin DUB – LAX (note: all BA flights are about $20 more).
Sat Nov 11 – Wed Nov 22
This same itinerary is available for $512 round trip through Momondo.com searches.
Los Angeles LAX – London LHR – Paris ORY/Paris CDG – London LHR – LAX
Sun Oct 15 – Thu Oct 26
In this example, better flight itineraries were found through BA website compared to those offered for the same price with Momondo.com searches.