The new Elizabeth Line service will be extended to Terminal 5 at Heathrow Airport, it has been announced.
A decision to boost the west London hub's rail links was agreed by Heathrow, Transport for London (TfL) and the Department for Transport (DfT).
In May, Heathrow chiefs lost a High Court challenge over access charges they can levy on Elizabeth Line trains.
Crossrail was named the Elizabeth Line in honour of the Queen.
From December 2019 Heathrow will be served by six Elizabeth Line trains per hour, two of which will run to Terminal 5.
This will increase the total number of Heathrow trains departing central London from 18 per hour to at least 22.
Legal action was triggered after the Office of Rail and Road (ORR) decided the amount which Heathrow Airport Ltd could charge Crossrail, and others, for using the spur could not include any amount connected to the recovery of the spur building costs.
The airport applied for a judicial review at London's High Court, arguing the decision was irrational and ORR had no power to reach any decision over the access charge at all.
But Mr Justice Ouseley ruled the challenge failed on all grounds.
Heathrow chief executive John Holland-Kaye described the agreement on increasing train services as "a big step forward".
He said: "Heathrow, TfL and the DfT are working together to boost rail connections to the UK's hub, giving our passengers more choices to travel sustainably between Heathrow and London.
"With 22 trains per hour, an ambition to add even more services and easy to use Oyster and contactless ticketing, Heathrow will be at the heart of an integrated transport network and our passengers will reap the benefits."