Question about customs in JFK and booking two separate flights

You go through customs when you first enter US regardless of whether one or two tickets. You also pick up any luggage you have checked in.

I would not do a two hour connection in JFK on two unconnected flights.

You also, most importantly, go through passport control at JFK when you re enter the USA. Do you all have Global Entry which gets you through quickly? If not, two hours is not enough time.
We always take the daytime flights out of BOS to LHR when traveling to Europe. The British Airways flight leaves at 7:30am. You arrive in London near dinner time, go to bed and wake up without jet lag.

"The British Airways flight leaves at 7:30am. You arrive in London near dinner time, go to bed and wake up without jet lag." Can this ever be a dream come true for us far from the coasts?

@Bruce, even those of us on the coast (e.g. me in Atlanta) can't do it unless we fly into Boston or NYC the night before, which you could do, too! :)

Also, no, we don't have Global Entry. So do you think a 4-hour window would be enough time between the two flights?

We have a similar situation coming up in April. We are using miles for a Boston-Paris round trip flight, the taking separate flights to/from Italy. For the flight from Paris to Italy we are allowing 5 hours between flights. I posted a question about this on the RS forum, and the consensus was to allow four hours for a connection.

Your risk on mupltiple tickets with change penalties are "black swan" events. Air travel "black swans" include weather, mechancial and crew delay/cancellation problems. Idealy you would not want to be on the last ATL-BOS flight of the day and even if later flight departs, getting everyone from the delayed/canceled flight is not likely.

It would be better (if cost effective) to do a mult-city booking with leg 1 being ATL - BOS, leg 2 being BOS- London etc. If you are on the same ticket, you are the airlines problem. I have also seen (and rejected) flights where on overnight in included as one leg.

What are the airlines in question here? JFK has a lot of terminals and it can be time-consuming to transfer between them, so you have a leg up if your KEF-JFK and JFK-ATL flights operate into and out of the same terminal.

If both flights are on Delta (which I suspect is the case), then you're probably OK: the KEF-JFK flight will operate into terminal 4, and the JFK-ATL flight will probably operate out of terminal 4; be aware there are a number of Delta JFK-ATL flights that operate out of terminal 2.

It's impossible to predict with 100% certainty this far in advance which terminal your flight will operate out of, but I'd attempt to make sure that your JFK-ATL flight leaves out of terminal 4 as well. This will improve your chances of making the connection and also just make it a little easier.

My question is, when we arrive in JFK from Reykjavik, do we go thru US
customs at that point, since that is the "final" US destination on
that particular ticket, or would we go through customs in Atlanta
after the JFK-ATL segment on the second ticket? Trying to figure out
how long of a "layover" we'd need in JFK to pick the time of the
return domestic flight.

Great plan about heading to London. My comments below are about your return.

Passport control and customs can take anywhere from 30 minutes at Terminal 4 if you're on Delta (you mentioned SkyMiles) to 2 hours. The walk from the arrival gate to passport control could also be a long walk especially if the people movers are broken. Think 20-30 minutes depending upon the speed of you and your children. After immigration you have to wait for your luggage and recheck them. The layover should be at least 4 hours. The good news is that since you'll be flying DL to ATL, you won't need to take the Airtrain. Chances are your flight to ATL will also be at T4. If it is at T2, you can take the airside Jitney to T2.

At JFK, find out from other Delta flyers whether you have to go through security again after immigration & baggage claim. That you will have to check in your bags makes me think that you will. Still, given that you won't need the Airtrain, if passport control and baggage retrieval do take 2 hours, you should still have time to go through security as the KEF flights tend to arrive by 1pm. Check in at least 24 hours ahead of time for your ATL flight and just go to the dropoff kiosk for your bags. Then head over to security.

You’ve removed the risk outbound by staying overnight. Coming home another story. My belief is there is no safe layover when flying with separate tickets. Yes, 4 hours might be enough but, as ha been pointed out, stuff happens. Are you prepared to buy 4 more tickets last minute to get home? Frankly, I’d take the 7 hour layover, get a club pass somehow. Or, do what you did outbound and spend a night in NY.

Good insights y’all! Yes, all flights would be on Delta. And we always carry on (no bag checking) so not concerned about that. It sounds like 4 hours should be ok.

Given that all of your flights are on Delta (or a Delta code share), check into booking all flights on one ticket.
https://www.delta.com/content/www/en_US/shop/deals-and-offers/north-america/multi-city-flights.html

Select “multi-city” while searching for flights, then follow the
simple steps to book your multi-city ticket. Also, use tools like the
Fly Delta app and your My Delta account to keep track of your
multi-city trip.

One question I'd consider is regarding your initial open jaw flights for each leg - are there alternative flights if something goes wrong? For example, if you are taking the last flight out of Atlanta to Boston the night before, you might be out of luck for your London flight if the Atlanta flight was cancelled.

I know that open jaw can be a cost savings, and if you have extra airline points, you might be willing to take a chance on having to pay for a flight leg if there is a problem. My daughters, aged 20 and 25, recently took a trip to the Azores and booked open jaw flights through Boston, thinking they'd save money. They "oh mom'd" me when I suggested that there could be an issue if a flight was delayed, since the tickets were separate. They thought they'd be fine, because they had planned an extra day in Boston both going and returning (staying with their brother, who lives there). It worked like a charm going out, but their return flight from the Azores was delayed for over 24 hours. When they finally landed in Boston, exhausted after having slept on the floor at the Azores airport, their flight from Boston to Columbus had already left. Delta's response was "oh well". To make matters worse, all remaining flights to Columbus for the day were already booked. (As I recall, that was the point where there were some tears.) They can laugh about it now, but just know that if things go wrong on an open jaw ticket, they can go very wrong....

Good luck, and enjoy your trip!

And as the OP already knows what he may find is that the cost in points is dramatically higher flying from his home town. So the “how to book open jaw” class won’t really help

As someone who has done this 4 hours should be plenty. Plus when you check in at REY tell them you have another flight home. Delta will generally link them together which will help if there is a delay

There is no need for Global Entry as many major airports have Mobile Passport Capability. To get through Passport Control when returning to the US, get the Mobile Passport App for your phone. It stores your passport info and a second photo of you on your phone. Before you land you put in the travel info and fill in an online customs declaration. When you have Wifi in the airport you press send and it will return a QR code to your phone. Find the Mobile Passport line and you are through Immigration and Customs very quickly. You can put multiple family member's passports, if they are travelling with you, on your Mobile Passport App on your phone.

Seconding what's been said above. Download the CBP Mobile Pass app on your phone. Fill in the relevant info before you depart (like passport details & you take a photo of yourself) to save the last minute stress of doing it when you land. Then when you land, you fill in the details of your arrival flight and submit that. Then hunt down the Mobile Pass line when you reach Immigration. (It was really difficult to find the first time I was there, but it's a breeze to use.)

That will save you a little time, especially if your first flight is delayed for any reason.

But I would never risk an international return at JFK on non-connecting tickets with a 2 hour connection. I wouldn't even feel comfortable if both flights were on the same PNR.

At JFK, find out from other Delta flyers whether you have to go
through security again after immigration & baggage claim. That you
will have to check in your bags makes me think that you will.

No need to check with other flyers — you always have to re-clear security in the US if you are connecting to any onward flight after clearing US immigration and customs. (Depending on the layout of the airport, there is often a transfer security checkpoint which might be faster than the checkpoint for originating passengers. But they're all subject to the same TSA rules and procedures.)

The only exception is if you're arriving from a destination with US immigration and customs preclearance (major Canadian airports, some Caribbean and Irish airports, Abu Dhabi), in which case you land into the secure area like any other domestic passenger and can proceed straight to your onward gate.

It's because you have to get your bags to proceed through customs, and so you could have had access to prohibited (carry-on) items in those bags, and so need to be re-screened. And of course we don't segregate passengers with and without checked bags in the baggage claim area, so everyone has to get re-screened regardless of whether they personally checked a bag.

Some really good thoughts/ideas/suggestions in this thread; thanks!

I've spent the morning trying to get it to work where I do an open-jaw flight with 3 legs (ATL - BOS, BOS - LON, REY - JFK) and it either gives me an "no points flights available" when I go this route, or, it won't give me the option to fly in Day 1 to BOS, spend night, and take morning flight out next day (it only gives me overnights from BOS to LON, with a morning ATL-BOS flight, which I don't want to do). Now if I called Delta I might be able to make it work, but I'm not that desperate yet, haha!

And, as a PP mentioned, the amount of points it takes from REY - ATL is much higher than REY - JFK, which is why I was willing to pay for the JFK - ATL leg. We will barely have the required amount of points as it is to take the trip at the lowest points level (50K/pp Skymiles). And I can't seem to get the "points + cash" option to work with the open-jaw option. But I don't give up easily! :)

In conjunction with our upcoming trip to Italy, I booked a Boston-Paris round trip flight on Delta using the pay with miles option (note: at the time of booking, I had a Delta AMEX credit card). The pay with miles option was only available with a Delta-operated flight, not with other Skyteam partners. I then booked separate flights on Air France for Paris-Venice and Milan- Paris. The Paris-Venice flight leaves five hours after the BOS-CDG flight arrives. The Milan- Paris flight is for the day before our return home. We will be staying at the Paris airport on the night before our flight from CDG to BOS.

It may also be possible to purchase additional miles if you are short.

My point is that there are sometimes a number of ways to solve an air itinerary problem.

You could try calling to see if you can get the "cash plus points" to work with your desired itinerary. Sometimes, in a case like this where you couldn't book it online, they even wave the telephone booking fee. But, even if you have to pay a booking fee, it's worth it to have the flight segments on one ticket.