Network Rail said it is conducting signalling, track and HS2 work between Paddington and Slough on Christmas Day and Boxing Day, which means no trains will be able to serve Heathrow.
Meanwhile, TfL is suspending the Piccadilly line between Heathrow and Acton Town for seven days from Christmas Eve.
We’ve worked hard with train operators to reduce the impact on passengers
Andrew Haines, Network Rail
The combination of the work being carried out by Network Rai and TfL means no rail or Tube services will operate to or from the UK’s busiest airport on Christmas Day or Boxing Day.
Public transport across the UK traditionally shuts down on Christmas Day, but services normally operate to and from Heathrow on Boxing Day, which is one of the airport’s busiest days of the year.
Heathrow introduced a £5 fee for cars dropping off passengers at terminal forecourts on November 1.
Mike Gallop, Network Rail’s western route and strategic operations director, said: “We’re in the business of delivering a safe and reliable train service to the tens of thousands of passengers who use services at Paddington every day.
“We need to spend 52 hours removing ageing and unreliable signalling equipment and swapping it with modern and reliable replacements.
“The very best time to do that is always when there are fewest people travelling. With no trains on Christmas Day and very few on Boxing Day, choosing those days clearly makes sense overall.
“Four years in the planning, and with good coordination and planning with TfL in place, a high quality and quick bus replacement will whisk what passengers there are, directly from central London to Heathrow.”
A TfL spokesman said: “The festive period is one of the quietest times of the year on public transport and carrying out these essential works on the Piccadilly line over this period will minimise the disruption as much as possible.
“We’d like to reassure customers that alternative travel options will be in place, with replacement coach services operating non-stop between Hammersmith and Heathrow.
“Replacement buses will also be available between Acton Town and Heathrow for local stations.
“We have been working with Network Rail on the comprehensive alternative transport plan and have also been working with Heathrow Airport to ensure they can support customers travelling to and from the airport on Boxing Day.”
Anthony Smith, chief executive of watchdog Transport Focus, said: “For passengers travelling over Christmas, engineering works are the last thing they want to hear about.
“Whilst the investment projects are welcome and most will avoid disruption to their journeys, closing the major rail and Underground routes to Heathrow on Boxing Day will still be a major headache for some.
“It’s crucial that Network Rail now works with all relevant transport and travel operators to help those affected, with a proactive approach to contacting those who have already booked travel.
“Communication of disruption must be clear and consistent across all available channels.
“This will ensure anyone planning travel is able to arrange alternative arrangements well ahead of the festive season.”
Other routes affected by Network Rail’s engineering work over the festive period include:
– Southern’s Gatwick Airport trains will operate to and from London Bridge instead of London Victoria between Christmas Day and January 3.
– Leeds will have a reduced service between December 27 and January 3, including a “very limited” service on January 2.
– No services between London King’s Cross and Finsbury Park on Christmas Day or Boxing Day.
– CrossCountry trains will not call at Bristol Parkway between December 27-31. Some Great Western Railway services to and from Bristol Temple Meads will also be affected.
Passengers can find out whether their journeys are affected through their train operator or National Rail Enquiries.
Network Rail said the 370 engineering projects it is carrying out over Christmas have been planned “months, and in some cases years, in advance”.
It added that more than 95% of Britain’s rail network will remain open.
Andrew Haines, Network Rail chief executive, said: “While some essential work is taking place to upgrade our railway over the festive period, we’ve worked hard with train operators to reduce the impact on passengers as far as possible so that they can spend time with their families and friends this Christmas.
“I’d like to thank the thousands of rail workers who will be working to keep services running, and those delivering upgrades to improve our railway and bring more reliable journeys to passengers in future.”