Rail links to Heathrow from central London will be disrupted over the last weekend of November.
There will be no Elizabeth line or Heathrow Express trains to the airport on November 25 and 26 due to essential works by Heathrow.
Piccadilly Line Underground trains will be the only rail connection to Heathrow Terminals 2, 3 and 4, but only buses will run to Terminal 5.
The weekend closures were confirmed by Transport for London (TfL).
TfL advised travellers using the Elizabeth line that the weekend closure “may cause some disruption” to their journeys.
“Parts of the line will be closed on Saturday 25 November and Sunday 26 November as essential maintenance works are completed by Heathrow airport, Network Rail and TfL,” it added.
“Due to planned Heathrow engineering works on Saturday 25 and Sunday 26 November, the Elizabeth line and Heathrow Express will not be running to Heathrow airport all weekend.
“Piccadilly line trains will be operating between central London and Heathrow as normal, serving Heathrow Terminals 2 & 3 and Terminal 4, but they are likely to be busier than usual and no trains will run to or from Heathrow Terminal 5.”
Elizabeth line director Howard Smith said: “We appreciate it is a complex weekend of closures with Network Rail, TfL and Heathrow airport all carrying out works which may cause some disruption to customers.
“These works were planned several months in advance and should help ensure that the Elizabeth line infrastructure operates reliably.
“Network Rail and HS2 are also preparing for their new railway and station at Old Oak Common which will also mean some future closures.
“I apologise for any impact on journeys over the weekend and would advise customers to check before they travel using TfL’s travel tools, and plan in advance as trains and rail replacement buses may be busy.”