Tickets to London

Go to your preferred airline’s website and buy direct from the airline.
You may want to compare a couple airlines to see which has a route and time you prefer and rates.
Enjoy your trip!

Start with Google flights to see what options it suggests. Then go to the airline’s website and purchase direct.

If you know your dates, go online and buy your Christmas at Kew tickets right away. It sells out fairly quickly.
https://www.kew.org/kew-gardens/whats-on/christmas

I second what Carol now Retired wrote. Google Flights for your options then buying directly from the airlines.

Will you be flying from O’Hare? I like British Airways.

I wanted to add some differences that go beyond the basic airline fare that you will want to consider.

Find out if your seat assignment will be complimentary or if will you be paying extra for it. Now if you don’t care where you sit on the plane this is a non-issue. If you do care, find out in advance what it costs to select a seat. Also be sure to know the baggage allowance associated with each fare.

Next, do you have a frequent flyer program that you actively participate in? There may be some advantages to choosing an airline within that Alliance.

If prices, seats, baggage, etc are all similar, then most people would prefer a non-stop flight .

Go to >https://www.skyscanner.net
Put in for flights FROM London TO USA - and tick Direct & select December - whole month. Yes, I know this seems odd to do this in reverse direction but doing it this way will bring up a whole load of USA cities with direct flights to London along with prices from.

Now start again in the ‘correct’ direction - select your nearest city and see how the prices vary with dates & note the airline(s). Then do it for your next most convenient city. Then go to the preferred airline website and book direct with them.

Another consideration regarding different airlines----what is the seat configuration for the route you will be flying? For example, we were trying to choose between Alaska and Delta, since Alaska has a new flight to London (We're in WA so we use Alaska a lot within our region; and, we've been happy with Delta to London for a few other trips.) The cost was fairly close (and we would've preferred the Alaska Dreamliner plane) but we ended up with Delta because just my husband and I are travelling, and we like the 2 seats by the window as opposed to 3 (fine if travelling with one of our kids).

I use skyscanner to find the various options, then book with the airline directly.

Thanks everyone!