Rail passengers were hit with travel chaos on Christmas Eve after rail strikes and staff shortages forced the cancellation of many services.
Staff shortages has also caused disruption on other routes including those run by Govia Thameslink Railway and Avanti West Coast.
CrossCountry had advised passengers not to travel on Christmas Eve or on New Year’s Eve, when more industrial action is set to take place.
General Secretary Mick Lynch said on Friday: “CrossCountry need to note the determination of our members in their action today and understand that they already have trained and competent guards that are available and ready to work.
“This dispute could have been resolved weeks ago if our members were simply allowed to get on with their jobs rather than having their long-term futures and their safety critical roles threatened by this cash-led assault by CrossCountry.
“The company have knocked back that sensible and rational approach and that’s why services are disrupted today.”
CrossCountry said in a message to passengers: “We’re sorry, but due to strike action by members of the RMT union, we are running an extremely limited service today.
“Your original train may not be running.”
Trains have been cancelled on the following routes by the operator:
Aberdeen and Edinburgh
Glasgow Central and Edinburgh
Derby and Nottingham
Leicester and Stansted Airport (a bus replacement runs between Leicester and Peterborough)
Cheltenham Spa and Cardiff Central
Newton Abbot and Paignton
Plymouth and Penzance
A reduced service is running between Edinburgh and Plymouth, Manchester Piccadilly and Bournemouth, and Birmingham New Street and Leicester.
One frustrated passenger who had to take a rail replacement bus said: “I’m more appalled that you could have warned us about this when we made the booking.
“If I’d wanted to travel by bus I’d have paid bus prices.”
Further disruption is expected on New Year’s Eve, when the strike will restart.
The AA estimated there will be 17.8 million cars on UK roads on Friday, as drivers making Christmas Eve leisure journeys and trips to buy presents compete for road space with commuters.
The worst queues were expected to take place in Wiltshire on the A303 between West Solstice Park and the A36, according to the RAC and traffic information supplier Inrix.
National Highways reported "severe" congestion on the M6 between Junctions 5 and 6 near Birmingham at 11.30am.
Airports were very busy as people rushed to get flights to destinations before Christmas with queues and delays reported at passport control at Heathrow.
The airport tweeted to a disgruntled traveller who had complained online: “Due to the increase of passengers Border Force are working hard to process passengers under new formalities, we appreciate your patience at this time.”
Further disruption is expected in coming days with Heathrow Airport cut off from the rail and Tube network on Christmas Day and Boxing Day due to Network Rail and Transport for London doing simultaneous work.