The third runway support is seen as controversial as many senior Labour politicians such as London mayor Sadiq Khan and cabinet members including Energy Secretary Ed Miliband have long opposed a third runway on environmental and health grounds.
In a speech on Wednesday, chief executive Thomas Woldbye is expected to say: "This privately-funded programme will upgrade existing infrastructure while laying the groundwork for a third runway, boosting UK investment and economic growth, with tangible benefits felt this year.".
Proposals for a third runway will be submitted to the government "by summer", the airport said, after Chancellor Rachel Reeves backed the expansion as part of her aim of growing the economy.
Heathrow is set to announce a multibillion-pound expansion plan to create extra capacity at the airport - as it prepares its proposal for a third runway.
Ed Miliband will find Heathrow third runway support 'uncomfortable' but he won't cause 'disruption', Harriet Harman says.
