Isle of Grain site for £50bn project is in middle of major flight paths for four London airports

A proposed airport in the Thames estuary would be in the "very worst spot" for the south-east's crowded airspace, according to the boss of Britain's air traffic control service, Nats. Richard Deakin, chief executive of Nats, said the architects of the Thames Hub airport had not contacted them beforehand to discuss its feasibility. Norman Foster and partners unveiled the blueprints of the £50bn project last November.

London mayor Boris Johnson has championed the idea of a Thames estuary hub in response to a growing clamour in the aviation industry and business for more capacity. The government has indicated that a much-anticipated consultation on aviation this summer will look at all options for airports except a third Heathrow runway, although the launch has been delayed until after the mayoral elections.

Deakin said the proposed site for the new airport, on the Isle of Grain, was directly under the convergence of major arrival and departure flight paths for four of London's five airports.

Pointing to the Thames estuary on a map, he said: "The very worst spot you could put an airport is just about here."

He said there were "serious challenges" to integrate an airport into that traffic pattern, and added: "We're a little surprised that none of the architects thought it worthwhile to have a little chat" with the air traffic controllers.

While Deakin conceded that "technically anything is possible", he said that beyond the well-documented risk of strikes from the thousands of birds found in the wetlands, the proximity of Amsterdam's Schiphol airport would also affect traffic patterns and force aircraft into more circuitous flight paths.

Such flight paths would run counter to much of the work being done to reduce fuel consumption in air travel. Industry bodies such as Sustainable Aviation say significant cuts in aircraft CO2 emissions could be made by planning more direct, intelligent flight paths.

He said that from an air traffic control point of view, "the single biggest thing we could do to reduce CO2 in the UK is to build a third runway at Heathrow".

Deakin claimed that the extra runway could cut the need for aircraft to hold in the skies before landing. "Heathrow holding is not about airspace – it's about lack of tarmac. I'm very confident you'd eliminate all the holding patterns in one go."

Pressure for new airport capacity has grown in recent months after intense lobbying from airport operators BAA and calls from within the Conservative party for the government to reconsider its opposition to the third runway – although a block on all airport expansion is explicitly laid out in the coalition agreement.

Last month the prime minister apparently gave fresh impetus to Boris Johnson's vision by announcing he would "examine the case for an estuary airport". David Cameron said Britain needed "to retain our status as a key global hub for air travel, not just a feeder route to bigger airports elsewhere, in Frankfurt, Amsterdam or Dubai".

The owners of Heathrow argue that there is a need for more capacity at a British "hub" airport – one big enough to allow enough connecting flights and transfer flights to make long-haul routes economically viable. However, they believe – and the Department for Transport's own analysis has concluded - that there is only room for one such hub airport in the UK, meaning that any Thames estuary airport would mean the closure of Heathrow and loss or relocation of 70,000 jobs in the M4 corridor.

Johnson's original "Boris Island" plan was for an airport at Shivering Sands, a few miles east of Foster's planned hub. He has said Heathrow is "fundamentally in the wrong place". Campaigners question the need for extra capacity. Environmentalists meanwhile have warned that any Thames estuary airport development would spell disaster for local birdlife, including protected species.

The Foster scheme, at the easternmost point of the Hoo peninsula, would incorporate a £6bn new Thames barrier crossing and a £20bn four-track, high-speed passenger and freight orbital railway around London, as well as new roads to serve an airport with four runways capable of handling 150 million passengers every year.

A spokesperson for Foster and Partners said that one of its architects, Huw Thomas, along with two members of the Halcrow engineering group collaborating on the project had since visited Nats' Swanwick HQ, in December 2011.

A DfT spokesperson said: "In the summer we will consult on an overarching sustainable framework for UK aviation and alongside this we will publish a call for evidence on maintaining effective UK hub airport connectivity. The coalition's position regarding Heathrow has not changed."