Opponents of the expansion of London City Airport last week called for the scheme to be halted as it fell within the current Public Safety Zone.

The cable car is set to extend across the Thames from North Greenwich to Royal Victoria Dock and has already had approval from Newham and Greenwich councils.

Transport for London halted the scheme to commission a report by the National Air Traffic control Services (NATs). That report has found the cable car will be safe for public use – even if the zone is extended.

A spokesperson for Transport for London said: “A national air traffic safety assessment has found that even considering expansion of City Airport, the probability of an aircraft accident affecting the London cable car would be less than one incident every 15 million years, an extremely low risk and well within safety guidelines.

“We have sent the report on to Newham for their consideration.”

Both Newham and Greenwich are expected to rubber-stamp the project before Boris Johnson gives final approval, but the delay may hamper efforts to build the cable car in time for the 2012 Olympics.

The Mayor has made it a key pledge as he seeks to build more river crossings in east London and believes it will benefit both residents and tourism in the area.

Jenny Bates, Friends of the Earth London Campaigner and one of those who lodged an objection, said: “A cable car would be a great, environmentally-friendly way of crossing the River Thames but it will pass through the expanded area around London City Airport needed to protect people from a plane crash.

“Friends of the Earth would like to support the scheme but it’s unclear how it avoids the Government ban on building in the crash zone – and whether the number of people at risk has been properly assessed.”