Layover in Keflavik

Almost certainly. Keflavik is a small airport and security is a breeze. They have been known to hold planes until everyone is on board. I had a 55 minute connection last year and made it with no problems.

I've done Icelandair a few times, and I think I figured out how they operate. In the morning they have flights arriving from all over North America. Then, about 60-90 minutes later they have a whole bunch of flights departing for European destinations. Then in the afternoon they do this in reverse. It's standard operating procedure for them. There's no problem making connections.

That said, the first time I flew Icelandair, we were taxiing to the runway getting ready to take off from SeaTac when someone got sick. They brought the plane back to the gate, removed the sick woman, then made us all deplane with all our carry-ons, and then reboarded us. By the time we arrived at Keflavik, most of us had missed our connections. I was heading to Copenhagen. They rebooked me via Oslo. I got into Copenhagen about 3 hours late.

So no guarantees, but you should be fine.

Yeah, I was worried about those short layovers too the first time I flew Icelandic Air. Mine was only 40 or 50 min. Everyone assured me it would be ok. I looked at photos of the airport, asked again on Fodors and Trip Advisor and everyone continued to assure me. Guess what, it was fine. Flying again next month.
As an FYI, the last few times, the bathrooms have been really crowded, so use the ones on the plane before you land.

Thank you for the replies. Will keep that flight as an option. Still prefer nonstop but the savings are significant.

Aer Lingus also flies from Newark to Heathrow with a change of planes in Dublin. The minimum stopover is 1 hr. 35 minutes, but they have flights going from DUB to LHR every hour, so you could select a longer layover. One of the reasons I like Aer Lingus is that you can go through US customs and immigration in Dublin on the way home.

Have you checked Norwegian? Nonstop flights from JFK to LGW. (Kennedy to London Gatwick)

There is no way I am going to go through JFK.

You'll be fine. A bit of advice, though: Use the bathroom on the plane because the one in Keflavik is hard to find, and there are a lot of people around, trying to find their proper gates. If you're alone, you'll have the added fun of having to drag your bag to the bathroom b/c you won't have a companion to watch over it.

I found the airport in Iceland a bit chaotic--and I'm not sure I'd fly with Icelandair again. Though the price was right (and still is).