plans are to fly JFK to Madrid - would rather fly Euro airline RT, but my top choices (KLM,
BA, AF) apparently contract with Delta/American for the outbound leg of preferred non-stop -
I'm hoping for feedback reflecting Fodors Forum satisfaction/dissatisfaction with the above-mentioned airlines, especially the US carriers (fyi: I have already gleaned what is available on other review sites)

And of course Iberia. We have mainly flown Delta, American and Iberia. If someone can distinguish between carriers than they are better than I am.

Go with the non-stop to Madrid airline.

KLM and AF code share with Delta. Select the flight that goes non-stop. They are all pretty much the same, though some planes may have better seat configurations than others.

Have used Delta a number of times to Europe with no problems and have also flown lines mentioned above. As mentioned above , they are all about the same

Flew AF using Delta miles to Paris and it was fabulous.

We have used Delta, Air France and KLM to Europe and liked them all. I would go with the best nonstop and seat configuration you like.

Use Delta between Manchester and Atlanta.

Best airline for economy without having to pay for a premium carrier like Singapore who are on another level for economy.

Get the economy plus seat for a little extra leg room. Was well worth it on flight to Munich from Philly.

Agree with flpab on the economy plus seats for transatlantic Delta flights. They don't cost that much more and make it much easier to snooze. We fly Delta (and its code sharers) exclusively and have have had generally good experiences.

I too have flown Delta to Europe several times and had good experiences.