Staff thought he was asleep when they encountered him during the trip.
When the train arrived at Bournemouth station, the workers realized that the man had not left.
Emergency services were called and the man was pronounced dead.
It is not known at what time of the trip the passenger died.
Reportedly, the man had a ticket to Stockport. This station is eight minutes from Piccadilly.
British transport police (BTP) have said the man’s death was due to a “medical problem”.
Her family has been informed.
Cross Country said that during the coronavirus pandemic, crews walked on trains, but due to social isolation, “contact” with passengers was reduced.
Since the onset of isolation, people have been advised to use transportation only for essential travel – or if they are a key worker.
A spokesman for the UK transport police said: “We were called at 2:41 p.m. at Bournemouth station on May 30 following reports of a sudden death on a train.
“The death was determined to be a medical matter and the person’s family was informed. ”
A CrossCountry spokesperson said, “The elderly gentleman had been seen by the train crew during the trip and thought he was sleeping, but when they did not leave at the end of the trip, emergency services were called who confirmed that the client had unfortunately died.
“Our on-board teams continue to cross trains as part of their duties, helping customers get around where they can.
“However, their interaction with our customers is currently reduced to maintain the recommended distance from others that we are all invited to observe. “