to then take another flight to AMS. Our flight is supposed to arrive at 11:30. I have not bought the tickets for LHR to AMS and in my research found a flight at 2:45 on KLM. Is 3 hours doable? We are only doing carry on. Thank you for your help.

I would think that is long enough. The LHR transit planner certainly thinks so:

https://www.heathrow.com/flight-conn...-MAY-2018/4/6A

and
That only applies if you have a single ticket with luggage checked through. OP doesn't, 3 hours isn't enough, 5 hours would be more sensible.

Good point. I shouldn't post late at night.

Both airlines use the same terminal (T-2) so IF you arrive on time, or even a little late, that would be plenty. But you have no control on whether you arrive timely, or whether there is a gate available when you do land.

Thank you all for the advice, I will look for a later flight.

But OP claims to only have carry-ons. In that case, OP only goes through the simple security plus the inter-terminal air-side bus if needing to change terminals. I'd be happy with 2 hours if not changing terminals, or 2.5 hours if changing.

Don, You are right, we are only doing carry on. I think the airlines are in different terminals so that will be additional time. If we land on time I would think we could make it but is that a chance that I want to take? Would you? I am so tempted to but the earlier flght...

>>I think the airlines are in different terminals so that will be additional time.<<

As I mentioned, both airlines use T-2. IF you arrive on time, you would have plenty of time. If you are delayed -- then you lose your ongoing flight and would have to buy a full fare, walk up ticket - and that is only assuming there are seats available. How does an unplanned night in London fit in the plans?

I have booked non-protected connections through LHR (changing terminals even) but it is a calculated gamble.

One good thing is you travel in May so winter weather delays/cancellations won't be an issue.

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Thanks Janisj, when I looked I thought Air New Zealand was T4 and KLM T2. I appreciate the feedback. I really would rather take the earlier flight.

KLM is T4 at LHR
Air NZ is T2 at LHR.
The terminals are quite some distance from each other.

There has been some juggling of airlines after T-1 closed and T-2 reopened so my info could be wrong

If in fact KLM is using T-4 - that is a bear of a transfer.

Thanks janisj. Good to know that and I am going to book the later flight. I would rather wait than eat the cost.

Why is there still doubt that KLM uses T4 at LHR? I fly KLM every 5-6 weeks in/out of T4 and have been doing so for at least the last 3 years. KLM have been flying out of T4 for around 10 years, if not longer. As for the transfer from T4 to T2, it can be done with the Heathrow Express, free of charge, it's very easy, however it is time consuming.

I've missed couple of flights from LHR over the years and have never had to buy a full fare ticket to get on to another flight. I've had to pay a change fee plus fare differential, but never a full fare ticket as suggested in this thread. There are flights every couple hours from LHR to AMS, the likelihood of an unplanned night in London is a unlikely.

I've made similar transfers at heathrow in less than 2 hours without issue, to be honest. Hell, for a 5 hour layover, you might even check taking the eurostar+thalys and taking the train lol.

No doubt you can make a transfer at LHR in less than two hours. The point at issue is whether you should plan on doing it.