Ryanair chief executive Michael O'Leary said expanding Heathrow was "not the way forward", urging the Government to "stop dithering" over additional runway capacity in the south-east and approve a three-runway solution in London.
On Tuesday (25 October), Heathrow Airport was given the green light for a third runway by ministers, beating Gatwick Airport following a lengthy consultation. The long-awaited decision was described as part of the Government's plan to "build a global Britain and an economy that works for everyone" and as a "major boost" for the UK economy.
However, O'Leary has called for Prime Minister Theresa May to approve runways expansion at Gatwick and Stansted as well, which would allow the two airports to develop additional runways as and when they see fit.
Granting expansion permission to two of the other London terminals would allow competition to encourage airports "to keep the costs of these runway developments down", the Ryanair boss added.
"Approving a third runway at Heathrow over Gatwick is not the way forward," he said.
"London now benefits from three competing airports [...] and the best way to deliver additional runways in a timely and cost-efficient manner is to approve three additional runways, one each at Heathrow, Gatwick and Stansted.
"The threat of additional runways at competitor airports will force Heathrow to keep its costs down while developing a third runway in the most timely and efficient manner."
O'Leary, who along with Ryanair has strongly campaigned for increased runway capacity in the south-east, said the decision contradicted the prime minister's pledge to make post-Brexit Britain a competitive and open economy.
"It's a return to monopoly featherbedding at Heathrow, and a continuation of runway capacity constraints in the south-east that will ultimately be bad for consumer choice and fares," he added.
Meanwhile, British Airways owner International Airlines Group (IAG), said it welcomed the decision to expand Heathrow and was pleased the Government had recognised building costs must not be passed onto the passengers.
In June, IAG chief executive Willie Walsh, accused Britain's largest airport of "ripping off" passengers amid new runway plans. However, Walsh adopted a more accommodating tone on Tuesday.
"We're pleased that a decision has finally been made but the cost of this project will make or break it," he said.
"The Government's directive to cap customer charges at today's level is fundamental.
"The third runway will be funded by airlines and their customers and does not come from the public purse. We will be vigilant in ensuring that Heathrow does not raise charges to benefit its shareholders to the detriment of the travelling public."