There's yet 7 hours until the departure of that flight. Presumably the airlines's operations department has not yet filed a flight plan, which tracking websites would be using to match a particular aircraft to the future flight.
However, I note that the flight you linked to (in a comment on Kate's answer) is BA 202, which goes from an overseas airport to the operator's hub in London. Thus there's a really good chance that it will be operated by an aircraft that has just completed an outbound flight in the other direction.
Searching on BA's website (for flights a week from now such as not to confuse it) we see that flights from London arrive in Boston on Fridays at 13:30, 19:35, 20:50, and 22:20, and leave at 07:50, 19:20, 21:35, and 22:40.
Evidently one aircraft stays in Boston overnight, so assuming they depart in the same order they arrive in, you want the one arriving at 19:35, which is BA 203. (As a check on this conclusion, the flight numbers are next to each other, which is usually the case for outbound/inbound flight pairs).
Flightradar24 shows BA 203 as a Boeing 777-200, registration G-VIIC, which is currently almost halfway between Ireland and Newfoundland (and expected to arrive about 20 minutes early).