Upvote:1
It's not something we could know without knowing your dates and flights. But yes, it can happen, you'll just need to investigate. Sometimes the sum of segments can be less than the total price.
ALso, do you have to use Delta? There are many trans-Atlantic airlines, consider an aggregate site like kayak which provides the ability to find flights with mixed fares - so you could find economy for the first part and business for the second, for example.
Sometimes it's cheaper, sometimes it's not. At that point you'll ahve to decide on whether it's worth it for you.
Upvote:1
On a trip like this, unless you have a really good reason not to do so, book a round trip instead of a multi city and fly the European section with a European airline. In case, book a BOS-BCN and a BCN-VCE roundtrip. You might find substantial savings. Or you might not but it worths a try. Use Skyscanner for the European leg, it knows about the low cost carriers.
If you do not stick to Delta then when I search for a BOS-BCN round trip on AA and pick business for one segment I see this:
And while Pricing and booking mixed-class fares, with economy & premium economy combined? says Kayak provides this as a possibility it also says it's not for every flight and for this one I was unable to do the picking there.
Upvote:1
It may be wise to just take the big hit on a business flight Boston-Barcelona return, then use budget carriers to travel within Europe such as Easyjet or Ryanair.
E.g. BOS-BCN, BCN-VCE, VCE-BCN, BCN-BOS
You will only have to book 2 return flights which could be cheaper than individual flights. I apologize if this is does not coincide with your schedule.