The agreement will see Elizabeth Line trains stop at Terminal 5, with two Crossrail trains serving the terminal every hour. The total number of trains stopping at Heathrow every hour will go up from 18 to 22.
That means a train will leave Central London for Heathrow every two and a half minutes.
Passengers on the Heathrow Express and TfL Rail between Heathrow and Paddington will also be able to use oyster and contactless technology to pay for their journeys from May 2018.
From 2026 passengers on HS2 will also be able to change to get to Heathrow by the Elizabeth Line at the Old Oak Common Interchange.
The moves are part of Heathrow's goal to have half of all journeys to and from the airport made by electric or low emission public transport by 2030.
When Crossrail fully opens in December 2019, there will be 12 Piccadilly Line trains (six to Terminals 2, 3 and 4 and six to Terminals 2, 3 and 5), Six Elizabeth Line Trains (four serving Terminals 2, 3 and 4 and two serving Terminals 2, 3 and 5) and four Heathrow Express trains, every hour.
An additional two trains per hour to Terminal 5 are also under consideration, as is western rail access to the Europe's busiest airport.
The airport is also working to improve the bus service network to ensure easier and more frequent access to the terminals.
Heathrow CEO John Holland-Kaye said: “This agreement is a big step forward. Together 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.”
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