An audacious plan to turn Birmingham Airport into the world’s biggest aviation hub capable of handling more than 70 million passengers a year has attracted an unlikely supporter – Boris Johnson, the mayor of London.

Mr Johnson said Birmingham’s proposal for a second runway was “on the button” because it made his own idea for a Heathrow-replacement airport in the Thames Estuary more likely to happen.

He told the newspaper that he welcomed Birmingham’s “support” for his scheme, nicknamed Boris Island, and added that there was now a general understanding that Heathrow could not expand any further because the noise impact in west London would be too great.

The London mayor’s comments came as Birmingham Airport and the Greater Birmingham and Solihull LEP made a much-trailed announcement setting out details of a huge growth plan based largely around the planned arrival of HS2 high speed rail.

If the expansion scheme was to be delivered in full, Birmingham could become the world’s largest airport by the end of the 2020s with 500,000 flights a year.

The vision represents an abrupt about-face for the airport, which ditched a planned second runway several years ago, declaring that the scheme had an insufficient business case.

A report issued today by the airport and GBSLEP councils describes the Government’s aviation strategy as misguided.

It accuses the commission led by Sir Howard Davies that is examining the future of UK airport capacity of being too focused on London and the South-east.

The report states that Birmingham Airport’s current capacity could immediately be doubled to 18 million passengers a year even without new infrastructure.

A runway extension to be completed next year will allow non-stop flights to China, India and the west coast of America and will give Birmingham a capacity of 27 million passengers a year.

Today’s report sets out a blueprint for growth at Birmingham Airport undreamt of in the past.

It’s suggested that the airport could become a “UK Central” international hub airport, overtaking Heathrow as Britain’s biggest, and able to handle as many as 70 million passengers a year with 500,000 flights.

By contrast, Heathrow currently handles 70 million passengers a year with 476,000 flights.

When HS2 is completed, the capital’s main interchange station in West London would be just 31 minutes away from Birmingham. It’s estimated that half of UK’s population will be within an hour’s journey time of Birmingham Airport.

Although Birmingham’s proposals are certain to attract opposition from environmental groups, airport bosses are keen to stress that an enlarged airport and second runway would be built within the existing footprint and would not require the demolition of any properties.

Paul Kehoe, Birmingham Airport chief executive, believes the UK’s long-haul traffic cannot continue to be routed through Heathrow.

Mr Kehoe said: “In 20 years’ time, British air travel will double. We believe that the best option is to create a network of long-haul national airports, each supporting the comparative economic advantages of that region to boost trade, foreign investment and tourism.”

However, an expanded Birmingham Airport may still find it difficult to drum up business.

Both British Airways and Virgin have stated that they do not believe a West Midlands airport could ever provide a viable alternative to London.

The Airports Commission headed by Sir Howard, the former chairman of the Financial Services Authority, is expected to publish an interim report before the end of the year on how aviation capacity can be improved.

The cost of the Birmingham expansion scheme will be published next month. The airport expects to attract some public sector investment and GBSLEP has already set out details of planned highways improvements.

These include:

• Remodelling of the M42 at Junction 6 to provide a dedicated junction serving Birmingham
• Airport. This would enable a segregated entrance/exit for the Airport, NEC, HS2 and other local road users to be provided.
• Widening of the M42 between Junctions 9 and 10.
• Direct access from the M6 to Birmingham Airport.
• Better road connectivity to major rail stations to enable passengers to travel by rail from key strategic points.

Other proposals by GBSLEP include investing in a new rail line bypass to take trains to the airport around Birmingham city centre using freight lines.

This would improve ease of access to the airport and reduce journey times by ensuring that passengers not seeking to visit the city centre could travel directly to the airport.

A report by the West Midlands Economic Forum -‘Stimulating Revival – the role of Birmingham Airport in rebalancing economic growth’ – concluded that expanding the number of flights and passenger through-put at Birmingham Airport could add 31,000 jobs on site and boost catchment area employment by 243,000.