Gatwick has criticised the government's decision to give Heathrow expansion the go-ahead, but said it "stands ready to proceed when the time comes".
The airport had been mulling over its response to the news and a few hours after the story broke, chief executive Stewart Wingate said: "We are disappointed as we do not believe this is the right answer for Britain.
"Gatwick has put forward a credible financeable and deliverable plan for expansion. It is a plan that can guarantee growth and guarantee certainty for Britain. We look forward to studying the full reasons behind the government decision in detail."
Read more: Give Gatwick go-ahead too, say businesses
He added that the challenges facing Heathrow "have not changed". A Gatwick spokesman told City A.M. the airport was going to "reflect on the decision" and now was not the time for it to launch a legal challenge, though it hasn't ruled it out.
Wandsworth council is joining forces with Windsor and Maidenhead council, along with Hillingdon and Richmond, to fight expansion with a legal challenge.
Wandsworth council leader Ravi Govindia said the Heathrow fight is "far from over" and the council is deciding its legal strategy going forward.
Gatwick has said before it will be on standby should Heathrow get the go-ahead as it anticipates its rival running into trouble.
The airport had been on all-out charm offensive to win over the government. Just yesterday, Gatwick chairman Sir Roy McNulty wrote to members of the airports sub-committee, saying that expansion at his airport was "the progressive competitive option".
"Give Gatwick the green light and we can help guarantee balanced growth for all of Britain," he said. "A London with two world class airports can send a powerful signal to the world that Britain is truly open for business."
But Heathrow was the chosen pick, with transport secretary Chris Grayling announcing the decision as a "truly momentous" step.
"A new runway at Heathrow will improve connectivity in the UK itself and crucially boost our connections with the rest of the world, supporting exports, trade and job opportunities," he said. "This isn’t just a great deal for business, it’s a great deal for passengers who will also benefit from access to more airlines, destinations and flights."