The £16bn Crossrail project has received a major funding boost after airport operator BAA agreed to commit £230m towards the scheme.

Heathrow Airport Limited, a wholly-owned subsidiary of the Spanish-owned operator, will put forward the cash in return for a guarantee of fast-train services every fifteen minutes linking the airport with central London and surrounding areas.

The financial package is subject to approval from the Civil Aviation Authority, BAA's economic regulator. If given the green light, it will be paid in two instalments dependent on construction progress of the Stockley Works, which will deliver greater reliability for Heathrow rail services.

Transport minister, Andrew Adonis, said: "Crossrail is the largest addition to the transport network in 50 years, and the announcement that BAA has confirmed a £230m funding package for the project represents a major step towards its delivery.

"Trains will run four times an hour for most of the day – cutting journey times across London and the South East, and significantly improving rail access to Heathrow for thousands of passengers and airport workers."

BAA's strategy director, Mike Forster, said: "This vital new link will directly connect the City and Canary Wharf to the airport, complementing our existing Heathrow Express service and taking thousands of cars off the roads."

Under plans for the Crossrail project, a new rail line will be established from Heathrow Airport and Maidenhead, Berkshire in the west, to Shenfield, Essex and Abbey Wood in the Borough of Greenwich to the east. The route will also incorporate underground stations in Central London, including Paddington, Tottenham Court and the Isle of Dogs.

Legislation allowing the Crossrail scheme, the result of a partnership between the Department for Transport and Transport for London, was given royal assent in July, with work expected to begin in 2010.