A cut in domestic passenger charges at Heathrow Airport has come into force.
Airlines operating UK-bound flights from the west London hub will now pay £10 less per passenger, which represents a saving of more than a third compared with last year's price.
Heathrow claimed passengers could save more than £500 million over the next 20 years if the discount is reflected in lower air fares.
The airport's plan to build a third runway has been chosen as the Government's preferred option for increasing capacity in south-east England.
Heathrow chief executive John Holland-Kaye said: "Heathrow promised to do more to help Britain's economy grow stronger. I'm delighted that we're able to come good on that promise with our new £10 domestic discount.
"Putting over £500 million back into the pockets of British families and businesses will help to spur growth in every part of the UK."
From January 1 departing domestic flight charges for point-to-point and transfer passengers fell by 35%, to £19.13 and £14.35 respectively.
This reduction is set to last through to 2037 as long as it is "in the public interest and there is a justification", a Heathrow spokesman said.
The airport commissioned economic consultancy Frontier to carry out research into the impact of the discount, which revealed that passengers flying to Edinburgh could save the most money at an estimated £6.2 million each year.
This is followed by Aberdeen (£3.9 million), Manchester (£3.3 million) and Belfast (£3.2 million).
Tony Hallwood, a director at Leeds Bradford Airport, said: "This is welcome news, showing commitment to invest in and grow regional air connectivity between Leeds Bradford Airport and London Heathrow.
"British Airways have now carried over 500,000 passengers on the London Heathrow route and the lowering of charges will help to stimulate further growth in demand."
The £500 million figure published by Heathrow takes into account its proposals for up to 25,000 more annual flights from 2021, which could see new domestic routes to destinations such as Newquay, Liverpool and Dundee.
A draft National Policy Statement setting out why the Government believes a third runway at Heathrow is the best airport expansion option for the UK is expected to be published in the coming weeks, with the launch of a public consultation.
From March regional airline Flybe will begin serving the airport for the first time. It will operate 40 flights per week to Edinburgh and Aberdeen.
:: Here are the total estimated savings for passengers through to 2037 as a result of the reduction in domestic route charges, according to Frontier:
Aberdeen £82 million
Belfast £66 million
Edinburgh £130 million
Glasgow £73 million
Leeds Bradford £18 million
Manchester £69 million
Newcastle £45 million
Inverness £23 million
Prospective new routes £52 million.