US to Europe flights using 2 separate airlines

...are there any potential problems I should be aware of if the two flight itineraries are separate?

The biggest issue is that if anything goes wrong, you are on your own and probably out the cost of the second ticket. So if your first flight to JFK is cancelled, you have no recourse with Iberia when that plane takes off on schedule without you. By contrast, if you travel on a "unified" ticket, and the first leg is delayed or cancelled, they are still responsible for the entire itinerary and are required to still ultimately get you to your final destination.

Of course, travelers roll the dice on this every day and it works out fine. Until it doesn't... And, you can hedge your bets (notice a lot of gambling metaphors here? There's a reason...!) and go out to JFK a day early, padding against any problems. The downside is that by the time you do accommodations, meals, etc. that extra savings you highlighted by purchasing two different tickets starts to evaporate.

I can only speak for ourselves, but we almost never travel on separate tickets. And when we do, it is with at least a day built in for extra peace of mind.

I fly into NYC a day or two early before a separate flight overseas. Then there’s no reason to miss the connection. On the way home usually we book the flight home with 3 hours or more layover or once spent the night at an airport hotel since we arrived at night. Once I booked us on a connecting flight with 1.5 hours between the flight from India to JFK then on to Tampa. It was a mistake that worked out fine. We were prepared to purchase a last minute flight home. Wouldn’t do that to us again.

If there is one glitch, and any flight is late and you miss the connection, you buy a new ticket at the going rate. Not the rate you paid.

I fly a lot and I won't do this unIess I have at least a day in between flights.

Even if you flew into JFK the day before, and knowing the rates of airport hotels, you probably aren't going to save much.

I fly from JFK to Europe because I prefer daytime flights. I always fly into JFK the day before and when flying back to JFK, I spend the night before a flight the next day to my final destination.

But I also have lots of hotel points.

Another caveat not yet mentioned is either of the flight times changing before your departure, impacting the connection.
I did what you propose, and for the same reasons, with flights to, and within, Canada. At the time of booking (about 6 months prior) I was going to have a long layover in Vancouver, BC- 5 hours. Then the originating flight was pushed to 2 hours later so I definitely "lucked out" that it still worked.
Have you tried a random Google or Kayak search, from your home airport to "Europe" and see if maybe there's a European city serviced by Iberia that could provide the connection to Madrid?

We have done this type of travel in the past and are going to do it again on a trip we are taking in March. As others have posted you need to arrive at least a day early and spend the night in the JFK area. Also do the same thing on your return. We add up all of the costs and see if makes financial sense to travel in that way.

....Of course, travelers roll the dice on this every day and it works out fine. Until it doesn't....... That is the main risk. Over many years we have done it on an infrequent bases. Mainly a short European connecting flight after the arrival from the US. We always allowed at least five hours for the connection and never had problem until four years ago. It caught up with us. Our initial flight from the US was cancelled just as the plane was about to start its roll down the runway. Lost the connecting flight in Europe since it took three days to get rescheduled. So it can happen.

In your case I would not put the international leg at risk. Lots of things can happen from Pittsburgh and there is no plan B.

Don’t do it unless as others have said you spend the night before your flight out. Our airport in Bend is third tier with very few direct flights to San Francisco or Seattle to catch International flights. It was never a problem using separate airlines until it was. Even with a 3 1/2 hour buffer we still missed our connection to Amsterdam which caused us to miss our connection to Athens. It was the trip from hell to be rerouted everywhere and we will always think kindly of the KLM agent that went out of her way to assist us (she was on her computer and then finally in other agents’s faces insisting there was space for us on a flight to Zurich) when United and other San Francisco airline agents refused.

We have done this many times and never had a problem.It always been Southwest for the domestic flights and they have no change fees.

I did this once flying to London through JFK.

I found a GREAT price from JFK-LHR and bought a separate RT fare Louisville to JFK. Everything was fine until departure day when there were severe storms in Louisville, and the distinct possibility some flights could be delayed by weather.
Mine ended up not being delayed and I arrived with not problem in New York, but I had some anxious moments earlier in the day.

That's the day in my life that I decided the price for peace of mind (being made whole if delayed) was much more than what I saved on that fare and I've avoided split fares since, unless I find incredible savings. and I've yet to find that.

You have to gauge the possibility of severe weather in PIT in the height of summer and whether you could be delayed getting to JFK for your flight to Spain.

If the Iberia JFK-MAD is the 845PM flight and the savings are significant, then taking a Delta flight at 7xxAM, would be something to consider. That gives you the 'back up' of the 11xx AM flight. ( And even a later flight that leaves a thin transfer margin)

Going the night before and spending $$ on hotel and meals likely negates a significant portion of the savings.

Will you be able to meet the Iberia carry on limit?
https://www.iberia.com/us/luggage/hand-luggage/

Thanks everyone for your helpful replies. I think I will play it safe and book on Iberia from PIT to MAD even if my flight options are more limited.

We do this from Seattle to Europe: Domestic carrier within the US, stay overnight by the departure airport, and the next afternoon we fly to Europe using miles. We are saving about $700/person after hotel and meals, and we also have a nice leisurely departure experience. You are on the right track assuming the $$ makes sense.

We have done this many times except we leave from Boston. We always fly from our home airport (buffalo) one day in advance. We are usually able to book a hotel either with points or we use a free night so the additional cost is minimal.

We are doing this with our last leg of our trip (a two hour flight back home, after our flight from the EU) We cover ourselves with an overnight stay, and most important of all; a good trip insurance policy. Even factoring in meals and a hotel, we will end up saving over $500 per person.

When we do book separate flights, and decide NOT to stay overnight, we make sure that there is lots of time between flights, and many lo-cost alternative flights available.

Iberia is in the same alliance as American Airways. American flies from Pittsburg through Philadelphia to Madrid.

Is there any way you can try to get booked on those flights with your points with Iberia? You'll be flying on their partner, American.

I do this constantly on the Delta family. I do not depend on the fact that the airlines are related and have a relationship to deal with things. So for my last trip for I did this I flew to JFK at seven in the morning, my flight to London was at seven at night, I spent the day working at the airport now if you weren’t working, you can go see something in New York probably but are there also hotel rooms you can get but I allow a ton of time on both connections.

What do you need to realize if your flight to New York is late and you don’t make your flight to Spain you will be buying a new ticket. Neither airline has any obligation to do anything to help you. Same thing on your return so allow a lot of our time. My rule is at least four hours and a will willingness to pay the price since the price of a new ticket from JFK to London would be rather expensive, I allow more time. coming back I actually allowed about four hours, because the flight from JFK to Atlanta while it would’ve been expensive, would not have financially ruined me

Considering I’m allowing about eight hours and numerous Delta flights from Atlanta to JFK before my flight to Europe departed I don’t feel the need to spend the night in New York before I do this. I know others will and that’s fine but I’ve never felt that need to, and I said, I do this a lot. I’ve also done it out of Boston

For me, it’s a no-brainer because I can often get a business class flight to Europe out of those two cities for less than a coach class flight out of Atlanta. (There are disadvantages to living in an airline hub.)

The mention of trip insurance above was a good suggestion.

Does the advice change any for flights within Europe rather than US to Europe?
I am considering doing this from Crete (Chania) to Athens, and then Athens to Amsterdam on Aegean and then KLM, with a 4 hour layover. It would spare us an expensive and unwanted overnight in Athens and solve some other issues for us too. But it makes me nervous, for all the reasons outlined here.
(I have to say, this Forum is some special kind of magic. I logged onto the Forum this aft to see if I could find any advice on the topic, and right at the top, here was this thread!)

My advice for doing this, even in Europe would be the same thing. Four hours and a willingness to pay the price. So if something happens schedule changes etc. and you can’t make your second flight what happens to your travel plans. can you afford that? can you live with that? If not, add more time.