New bus connections now get you from Amtrak’s Vermonter at the Windsor Locks station right to Bradley Airport (Hartford) in Connecticut and from the train to the Big e in West Springfield. They also connect from the Valley Flyer Amtrak services from Greenfield MA.
Another bus runs from Springfield train station (berth 24) to the large big e fair. As you may know, traffic around the big e is a horrendous big deal, but the bus has a secret back door, making it terrific option (you don’t pay for parking and the bus shuttle is free). All the information is here: https://trainsinthevalley.org/trains-to-the-big-e/
The bus to Bradley has a catch: it will wait for late trains, but only up to 10 minutes. Therefor we recommend you only use this option from the Vermonter if you are prepared to order up an Uber/Lyft if the train is late. Don’t schedule your flight too close. More information on the bus to Bradley is here: https://trainsinthevalley.org/how-to-get-to-bradely-airport-on-public-transit/ Bus fare is $1.75 (much cheaper than parking).