I’m looking at flights to Krakow from Chicago. One flight is on British Airlines with a connection time of 2 1/2 hours. From my research so far it looks like I’d need to transfer to another terminal. Is this enough time do you think? It would be on a single ticket with carry on only.
British Airways recommends 4 hours between flights, but with no luggage to collect, maybe? LHR website says it's 20 minutes from Terminal 5 (where your flight from Chicago likely arrives) to Terminal 3 (where your flight to Krakow likely departs). When is the next flight to Krakow, in case your arriving flight is delayed? Have you looked at flying direct from Chicago to Warsaw instead? LOT offers that. It's easy to get an onward train to Krakow.
If this is all one ticket, then 2.5 hours is enough. BA would be responsible for getting you to Krakow if your flight from Chicago were delayed.
It depends. Are you booking both flights as one ticket? If separate bookings then I generally allow 5 hours in between flights. I would be comfortable with 2.5 if booked as one ticket. In the later case if you miss your connection BA would be responsible for getting you there on the next flight with availability.
https://www.britishairways.com/content/information/airport-information/flight-connections
British Airways recommends 4 hours between flights,
That is what BA says when you have separate tickets. The OP is looking at a single ticket.
https://www.britishairways.com/content/information/airport-information/flight-connections
Go to this website:
http://www.heathrow.com/fllight-connections
It will give you step by step instructions on what you need to do.
It's really simple. When you exit the plane, you follow the purple "Flight Connections" signs. You will take a bus airside from T5 to T3. Then you will go through security. After that you are off to your gate. No immigration, no customs.
We have connected through Chicago many times. We have NEVER had a flight depart on time. Never. Ever. Last month we were supposed to arrive home to our small regional airport at 10:50 pm. Due to a staff change and then mechanical issues in Chicago, our departure was late, and we arrived home at 2:20 am. My husband and I said we didn't care anymore how much more it cost to connect through Minneapolis instead of Chicago. We are just paying it.
I know you are not connecting through Chicago--simply departing from Chicago. My point is, do not plan for your flight to depart on time.
You should be fine so long as it is booked on one ticket.