I think I've finally realized why I can't stand fivethirtyeight.com. I was reading an an analysis which
purports to tell you how to fly between places the fastest. Except they ignore the critical component in fast flights - is your flight direct or is there a connection. Direct flights are faster. Connecting in some airports is better than others. (They also ignore another critical component when making travel plans - the money vs time element. Money is often the key driver in whether you will accept a connection. One hour flight time for $1000 or six for $200. Make your choice.)
Every time you add a flight segment you are adding a chance for a misconnect (particularly when you fly at times when the network is near capacity like Christmas) but the connection itself is going to add time. If you are lucky you will land in the same terminal, but if you are travelling from a small regional airport you are likely going to need to walk between terminals and sometimes it's a good 20 minute walk.
If you were flying out of Montgomery, AL you have two choices - Dallas/Fort Worth or Atlanta and then connect to whereever you really want to go. Dallas gets a red slow rating while Atlanta gets a yellow medium rating. Atlanta is a special bit of hell for connections and I'd avoid it at all costs.
I routinely fly out of the joy that is Heathrow. Based on airport experience alone, I'd rather travel out of most any other London airport, but Heathrow is the place to get long haul flights direct to the US. If I went to Gatwick or London City, I'd generally face flying to a European hub (in the wrong direction) and then changing to the long haul flight. The Heathrow circle before landing is notorious, but my door to door is still far shorter without a connection.
Basically, they used statistics to tell us nothing useful.