Heathrow chief executive Colin Matthews said the airport envisaged passenger numbers increasing from just under 70 million now to around 72.6 million by 2018/19.
He had admitted that Heathrow, airlines and the CAA had all got their passenger forecasts wrong for the period 2009 to 2014.
The CAA based their ruling on the charges Heathrow could impose on airlines on the basis of the west London airport handling 78 million passengers a year by 2013.
Mr Matthews said this miscalculation had resulted in Heathrow receiving around £650 million less in charges over the last five years.
This was money that the airport could not recover now or in the future.
The planned investment until the end of the decade is in addition to £11 billion that has been invested since 2003.