A £500 million investment on the Great Western main line has been given the go ahead, cutting journey times into Heathrow Airport for travellers across the west of England and Wales.
Journey times will be cut by 30 minutes for travellers from south Wales, the west of England and the Thames Valley when they will no longer need to travel via London Paddington.
The new stretch of track will be built from Slough to Heathrow.
The department of transport said the exact service had yet to be decided, but it would be possible, for instance, to get on a train at Cardiff and travel directly to the airport.
Transport secretary, Justine Greening, explained: “We are providing funding for a new rail line from the Great Western main line near Slough to Heathrow which could provide significantly improved connections.”
The development is part of winder government aviation plans and is expected to be operational by 2021.