Are both flights one the same ticket/booking? If you miss the last flight and are rebooked the following morning (given it’s most certainly the last flight of the day) would that be an issue for you?

It will take you an hour to reach Victoria(assuming tubes are running fine and no delays) and another 45 minutes(approx) to reach Gatwick from Victoria.I do this quite often on Fridays. These are travel times only. Clearing Heathrow immigration should be your main sticking point. 1850 hrs is busy time so if you can go through the e-gates you might be just about fine. But if you get stuck in the queue for manual passport check you might be in a bit of trouble. Try walking fast after disembarking from the plane.

What nationality are you? Will you have bags? Are all flights on the same ticket?

@jcaron I made the booking through StudentUniverse as a single unit, but the 3 legs are on separate airlines. I'm not sure if that qualifies as "the same ticket/booking." I would be okay with up to a 36 hour delay, though that's obviously not ideal.

You should have somewhere a "e-ticket receipt". If you have a single e-ticket number that covers all flights, then it's a single booking. If you have several numbers, then they are separate. Another option is to use the "manage my booking" section of the airlines. If any of the airlines show both flights then it's a single booking.

@DumbCoder I just realized that I made a mistake; the times are AM, not PM. Also, I would likely be taking the national express coach, which takes a bit over an hour of travel time.

@Doc US citizen. I'm almost certainly going to have one or two checked bags. Currently not sure if it's all on the same ticket, trying to figure that out right now.

Are there more flights from Gatwick your destination later in the day?

The two big issues are whether your incoming flight is on time (long-haul flights usually have quite a bit of padding, but they are not immune to delays, especially if you are leaving from an area in the US subject to big weather disruptions) and any queue at immigration. If you are on the same booking the airline will rebook you on the next available flight. If you are not on the same booking, then you're on the hook. Travel agents which sell independent tickets usually have some form of insurance bundled in to cover that, but in practice...

@MJeffryes There are other flights later in the day. None of them are on the same airline though; not sure how much of a difference that makes.

@TheGuywithTheHat Can you tell us the airlines and airports involved? Full service airlines will usually rebook within their alliance if you miss a connection, and if there are no convenient flights within their alliance, they may rebook with unaffiliated airlines

@jcaron Thanks for your help. I checked on british airways' website, and it currently lists both legs (the 1st and 3rd) under one booking.

So a few points to clarify why some of the questions are being asked as they may not be obvious for a novice traveller. Where it is all one ticket, and particularly with one airline, then (in general) they are on the hook for getting you to the final destination (and therefore won't book you on a connection you probably can't make). Therefore, when doing a "self connect" many people would look at longer layover times to account for delays. If your airline will rebook you (BA do it to other airlines), then there isn't so much need.

@MJeffryes The first leg is on Jetblue Airways from my hometown to JFK. The second leg (the new one that I'm being offered) is on Iberia from JFK to LGW. The last leg is on British Airways from LGW to DBV.

@Richard Thanks! I figured out most of that based on what everyone else was saying, but I appreciate you explicitly clarifying.

@TheGuywithTheHat It's not obvious, but Iberia and BA are actually the same company. In fact, the JFK to LHR leg will almost certainly be operated by BA.

@MJeffryes Okay, so that means that if I miss the connection then it's essentially "their fault," and they'll figure out some other way to get me to my final destination (at no significant extra expense to me)?

Yes, it would be responsibility of the airline (but to be clear, even if they were separate companies, it would be either the airline or travel agent's responsibility to get you to your destination regardless).

@MJeffryes Okay, thank you very much!

@DumbCoder Checking the traffic on Google Maps at that time, the 1 hour estimate from National Express seems accurate.