It states that the mayor's plan must conform to government policy and not oppose the scheme. London First director of planning and development Judith Salomon said: "The panel is reining the mayor in on Heathrow."
A spokeswoman for airport operator BAA welcomed the panel recommendation. "London cannot maintain its status as a premier business centre without world-class air links," she insisted.
But a spokesman for the 2M group of councils opposing the expansion countered: "This shows that nobody is allowed to come up with a policy against Heathrow. But it is an opportunity for the mayor to stick to his guns."
The panel said the plan should not prejudge the outcome of ongoing research into Heathrow's expansion.
Meanwhile, the growth of London City Airport could be set for a review after the London Development Agency (LDA) said the go-ahead for Crossrail raises questions about its long-term viability.
The airport needs LDA land to expand. Agency chief executive Manny Lewis said it is working with Design for London on plans to build a community in the event that the airport does close.