An unspecified number of Heathrow Express trains have been withdrawn from service after a fault was discovered.
The structural defect on the underside of the carriage found during a safety probe means that the rolling stock will not run for the “foreseeable future” and will undergo further examination and maintenance work.
A 15-minute service is being maintained to the airport using alternative trains.
Pre-purchased Heathrow Connect tickets will be accepted on the Heathrow Express, and the 140 bus between Heathrow and Hayes & Harlington.
They will also be accepted on the London Underground between Paddington station in London and Heathrow.
Heathrow Express tickets, which will be reduced during this period, will be required to travel on the non-stop service as usual.
A single ticket will cost £17, and a return £28.
Heathrow Express director, Fraser Brown, said: “The safety of our customers and colleagues remains our top priority.
“We apologise for the inconvenience this has caused so far, and assure passengers that we are doing everything we can to return to running a full and safe service, as quickly as possible.
“We would like to thank all our customers for their patience.”
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