Well, you all helped me get my daughter to Europe, now I am trying to get her back. Barcelona to SFO with a layover in Newark. Some of the layovers are less than 2 hours. More like 1 hr. 33 min. and 1 hr. and 45 min. This makes me nervous. What is reasonable for EWR.

I would be uncomfortable too. Lately passport control has been quick but I've had to wait up to an hour. It depends on how many planes are coming in at one time. Is she changing terminals in Newark? If so 1.5 hours will be dicey. Even if she gets through passport control quickly she still has to wait for her luggage and then she may get unlucky and have to put her bags through the agricultural screener and perhaps have them hand checked as well. This doesn't take much time but it does take a few minutes, especially if there are a lot of people being pulled out for the agricultural scanner.

If she is arriving into Terminal B and departing from the same terminal she does not have to go through security again. There's a transit corridor.

Need a little more info to offer a considered opinion -
what airline arriving and continuing?
what day/time?
will she have checked luggage?

I wouldn't be comfortable, unless she only has a carry on. She has to claim bagagge to go through customs and that can take a while.

I don't like anything under two hours no matter which East Coast airport I'm arriving at when coming from Europe.

United at 2 pm. I haven't booked anything yet. Many of the flights continuing to SFO have four digits, so appear to be code share. I will probably play it safe and allow more time. Thanks.

Is there a big price advantage to buying this itinerary? If not then allowing a longer cushion is not a bad idea. But if it is a big saving you're probably OK. If it is United all the way, booked on a single ticket, even if there is a misconnect (e.g., delayed arrival from BCN) she would be accommodated on the next available flight. This is hub to hub travel so there are likely plenty of flights - at least 4 or 5 nonstop flights plus other options to connect via IAH or ORD. And the four digit flight numbers do not necessarily indicate a code share, BTW.

Bollocks to anything less than 3 hours. Seriously.

Newark is an unholy mess going through security as an embarkation point and the US government has been squeezing resources for customs and immigration control at major airports in response to The Sequestration because the bureaucrats won't cut the back office fat.

And the "next available flight" may be hours or a day away - just because EWR is now a major United hub doesn't mean that missing a flight means you'll get a quick reschedule. The price of fuel and the airlines miniscule margins mean that flights are generally full to oversold.

Newark is a complete madhouse. We had a similar tight international connection (with 2 small children no less) and it was just an excruciating process with the intense pressure to hurry. As we realized we were probably going to miss that flight anyway, we just gave up, relaxed and tried to fight our way forward (without getting trampled by the thousands of other passengers in the same situation). If she can do it without checking luggage, she'd be much better off. If she can operate with a certain amount of zen and deal with being rescheduled on the next flight, she might be fine as well.

She is only 20 and this will be the first big trip by herself. I wil allow plenty of time.

When we have had a right connection from international to domestic at EWR, the agents let us cut the line to go through security faster.

Our last international>domestic connection at Newark in January (all United, mid afternoon) took one hour and 40 minutes from the time the door of the plane opened until we were through security in the domestic terminal...and we have Global Entry and access to priority security lines (but did have a checked bag). It was a real mess.

I booked a ticket for my daughter (also 20) to return from Lima via Newark in a few weeks, and I bypassed a possible 1:30 connection in favor of a longer one.

Sorry to say that I agree with BigRuss and Woyzeck: Newark is a mess.

I just back from Italy and had to use Newark to get my last flight home to Albany, NY.

When I had go through security at Newark after coming back from Rome, I did the usual thing after showing my passport and boarding pass near the x-ray machine and emptied my pockets and stored my last items in my carry-on bag, which was on the conveyor and about to go through its own security check. As I was about to enter the large x-ray machine, some fool asked me for my boarding pass. What? It's in my bag, I told the jerk, where it's supposed to be. Moreover, idiot, I added, I just showed it seconds ago to another clown a few feet away. Suddenly I've changed identities, become a possible terrorist threat in the short transit from that first checkpoint to the x-ray machine? I've never had to show my boarding pass twice, I told the idiot, especially when I not supposed to have anything on my person as I being x-rayed. Another passenger nodded, saying he'd never been asked to show his boarding pass right before being x-rayed.

I had a long layover in Newark. I observed a lot. There are workers there who do absolutely nothing for hours. I had the time to watch them.

If you need information at Newark, you have to be persistent. You'll often find fools who have no idea what's what.

Oh, and if you happen to be in Terminal A, good luck. It's hell, with crappy food courts.

BigRuss is absolutely correct, but I'd go further.

Right now, regardless of whether it's a "legal" transfer or not, you should not accept anything less than 3 hours if you are transferring from an international flight to a domestic flight at any major EWR, JFK, LAX, ORD, SFO, DFW, ATL, or MIA. This is because the sequester is causing extensive delays sporadically at all major airports in immigration. I had a fairly quick wait at JFK in March (about an hour), but waits of over 2 hours are not uncommon on really busy days, and 3 hours have been reported. Similarly, it's not at all uncommon to wait 30 to 45 minutes in security at EWR on a busy day. When you add up all those delays, it's easy to see how you simply can't do a 2-hour layover any longer.

Not all airports are equally bad, but I've tried to single out the busiest because they tend to have the worst delays, which vary wildly. You might come in and wait 10 minutes at one time of day, but you'd have to wait 2 hours if arriving 30 minutes later.

I am looking at a 4 hour layover for her. Thanks.

Changed our plan. Barcelona to Frankfurt then on to SFO.

I'm not fond of the Frankfurt airport either for transfers, but it's going to be much better than EWR. I think this is a good change for you.

My last experience in Frankfurt (Summer 2012) was pretty bad as well, but some of that was related to the construction on Pier A, as well as slow and understaffed security checkpoints, and cramped boarding gates (United/Lufthansa). While not as bad as Newark, I hope Michelle Y left enough time for the transfer.