TOD - I remember neither my first train nor my first plane ride, but have heard my mother talk about both so much it seems I do.
Train: When they received word that my father was being transferred from Portland, Oregon (where I was born), to Detroit, my mother wanted a farewell visit to the San Francisco Bay Area (where they'd lived before I was born). She and I took the train from Portland to SF and back - a trip I'd like to repeat now that I'm old enough to remember it (before I get too old to remember anything!)
The first train trip I remember was when my Camp Fire Girls group went from Plymouth, Michigan, to the state capitol in Lansing. We visited then-governor G. Mennen "Soapy" Williams in his office and shook hands with him.
Plane: General Motors (who transferred my dad) flew our family to Detroit, which, according to my mother, was the trip from h***.
The first plane trips I remember were on private planes. One of my dad's co-workers took us for a ride over Mt. Desert Island, Maine, where our family was on a camping vacation when I was 12. When I was in high school and we visited my aunt and uncle in Owensboro, Kentucky, he took us flying over the area where my dad grew up.
The first commercial flight I remember was when my mother and I flew to NYC for my first visit there, 40 years ago. At age 16, I had my first cup of coffee courtesy of American Airlines. Been hooked on coffee and NYC ever since!