Which airline would you fly Chicago to London Heathrow?

If any of these airlines have a daytime flight from Chicago to LHR, I would choose that one. There used to be a flight out of Chicago that left in the morning and arrived to LHR around 10pm. I take a daytime flight out of Dulles and strongly prefer that to any overnight flight.

For any of these flights, you can take the Piccadilly line to Hammersmith. At Hammersmith, switch to the District line (opposite side of platform) and continue to St James’s Park.

I wouldn't choose the airline based on convenience to hotel. There might be a slightly longer or shorter walk to the tube station depending on what arrival terminal but the the journey into the city is the same otherwise. If you haven't considered it you might see if American is still flying the daytime flight. It might seem like you are missing a day in your trip to do that, but if flying in coach it is a great alternative. I have done it a number of times both ways and prefer the daytime flight if I don't have the lie flat bed in business class. You leave ORD in the morning, enjoy the flight time with movies, reading or podcasts or whatever, arrive LHR in the late evening, go to bed when you get to your hotel and wake up with much less jet lag IME. Because late evening and you might just miss last tube departure from LHR I would use a car service like justairports.com from airport to hotel.

With BA you will get protection through UK 261, whereas you won’t on the way out with the US airlines.
I would also agree that a daytime flight is preferable.

Some people will have personal preference as to one airline over the other. It's really just personal choice.

To get to St. James Park tube station from Heathrow you would take the Piccadilly line to either Hammersmith or Barons Court and then cross the platform to get the District line to St. James Park. It's the same for any terminal at Heathrow.

There is a tube station underneath Terminal 5 while Terminals 2 & 3 share a tube station in between the two. It's a five minute walk from either terminal via an underground walkway. Very simple.

If you have no allegience to any airline, go with the one offering the best price and times.

Not much difference in getting into town. The main underground station is at terminal 2/3, but probably about as easy to get on at Terminal 5, which is the end of the Piccadilly line, with Terminal 2/3 being the next to last stop (Well, there is a Terminal 4 loop that does not apply here)

To get to your stop, I recommend just getting on the Piccadilly Line, take that to Hammersmith Station, get off, walk across the platform and catch the next District Line train, and take that to St. James Park, easy. Forget any nonsense about the Heathrow Express or the Elizabeth line.

Thanks for the quick responses everyone!! I appreciate the info. It sounds like no one terminal is “bad” so I will take Frank’s advice and look at time and price.

I personally don’t like the idea of a morning flight with a late evening arrival. I feel safer arriving in the daylight. 😊 Plus, I don’t mind the overnight flights. I don’t have any issues with jetlag other than being tired on my arrival day.

I do this flight frequently - a couple times a year.

I, personally, avoid BA. Over the years too many little issues or strikes.

I compare the prices and times of United and American. I've used both recently. Similar service level in my experiences. There is a flight that arrives at LHR around 11 pm. I have taken that and then stayed at a Heathrow hotel - I agree I don't want to be arriving at any city in the late hours and need to head to my hotel in a city center. Otherwise I take the Tube into London about 7 AM and arrive most often long before I can check into the hotel - even with high status at my hotel. Tube is easy from terminal 3 or 2.

While I fly from NYC, I always take the daytime flight as I will be doing next week. I arrive in the evening but I spend the night at an airport hotel. (Sofitel for T5, Hilton Garden Inn for T2 or T3.) Both are just a few minutes walk--inside--from exiting customs.

The next day I get up, have a free breakfast thanks to hotel status, then head into London after rush hour.

I don't sleep on overnite flights so I feel more rested taking the daytime flights.

YMMV

ORDtraveler, I appreciate the info. With an early am arrival in London, I will just reserve my hotel for an extra night so I can check in right away.

Frank, I don’t sleep on the flight either, but I’m somehow still able to function on arrival day.

I do exactly as Frank does. I fly BA on the day flight, but from Boston to Heathrow terminal 5, and overnight at the Sofitel. The day flight beats even an overnight flight in business class by far…for me. I will never take an overnight flight ever again.

Re booking extra night at hotel to guarantee early check in. You may want to contact the hotel and let them know your plan. Otherwise they may think you are a no show the previous evening.

I will just reserve my hotel for an extra night so I can check in right away

You MUST coordinate this with the hotel. Every night, hotels do "night audits" closing out the books for the day. This happens for most hotels around 2 AM. If the hotel doesn't know you are coming, they will cancel your reservation as a "no show."

By letting them know, they will check you in to make sure your room is ready. If your hotel offers online check in, that is NOT good enough.

Rocket and Frank, yes, of course I would let the hotel know. 😊 Thank-you both for checking to make sure I know this.

I've probably flown from Chicago to Heathrow some 20 times in the last 30 years. I personally have had good luck with British air but I would look at the actual cost and convenience of the flight times. As a senior citizen, I feel more comfortable taking a late afternoon or evening flight and arriving in London in the morning. I don't usually have a jet lag problem. On my latest trip for next week I found out I could get early check in at my hotel for $35. I will go to the hotel, drop off my luggage and clean up, have breakfast/lunch and pick some casual sightseeing nearby, and make sure I stroll in the area, have a nice dinner and then I'm ready to start heavy duty sightseeing the next day. These casual first days have led to many great experiences as London is such a fascinating place.
I book FAR in advance the Heathrow Xpress direct to Paddington Station --actually less expensive ( IF you book in advance) and more convenient. Paddington has good access to the tube and the new Elizabeth Line. By the way, I used the Elizabeth line last year-- very impressive. More stations are operational now. Be sure you have the most updated information when planning to use the Elizabeth Line.
By the way I was in London last year during the week of the queens funeral and I stayed at a hotel near Paddington, the Novotel London Paddington, and I am going to stay there again next week. It's only a six minute walk from the station and it feels Like a very safe and easy area to walk in even at night.

I have also stayed at the Novotel Paddington and used the Heathrow Express booked in advance for reasonable rates. Very comfortable transport; the farther out you can book, the cheaper.

I enjoyed my stay at this Novotel, but I should indicate that I stayed when on a business trip in the area. Although I would definitely stay again, it is perhaps not as convenient for a typical tourist as some other areas. As noted, easy walk to Paddington Station with great tube connections. Single female, never felt uncomfortable although traveling in January when it was often dark.

I just had to chime in - I don't see many positive plugs for the Novotel Paddington or the H'Ex. When the combination works for the itinerary, it is a good match.

The cheapest with the best schedule. All things equal, if I am correct BA has a higher carry on weight limit. So that one.

I appreciate the recommendations for the Novotel Paddington, but I’m pretty set on the Westminster location.

if I am correct BA has a higher carry on weight limit.

I’m a proud bag checker. 😊

Mister E--Wow! I just checked. BA has a 23 kg/50lb limit for each---carryon and personal bag. Wow!