Incredible £10bn train line that would connect Heathrow and Gatwick airports
The construction of the train line would cut down the journey between the two airports to just 15 minutes.
A high-speed train running directly between Heathrow and Gatwick would have been a dream for many travellers. A fast and simple link between the UK’s two busiest airports could have transformed the way people move around the South of England. And for a short time, it looked like it might happen.
The idea was called HS4Air. It was proposed in 2018 by British engineers Expedition Engineering and was promoted as a £10billion project that would finally connect the major high-speed lines running across the country. But despite the interest it generated, the plan never went ahead.
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HS4Air would have created an 87-mile route linking High Speed 1 (HS1), which runs from London to the Channel Tunnel, with the under-construction High Speed 2 (HS2).
Trains would have curved around the south and west of London, roughly following the M25, with new stations serving both Heathrow and Gatwick.
The project promised huge benefits. The journey between the two airports would have taken around 15 minutes, and passengers travelling from cities like Birmingham, Manchester and Cardiff would have been able to reach each airport without passing through central London.
Supporters said it would also reduce pressure on the capital’s transport network and offer a smoother journey for international travellers.
According to the plans, around 40% of the line would have reused existing railway tracks, with upgrades needed at Tonbridge and Ashford International.
About a fifth of the route would have been placed in tunnels to limit disruption to the North Downs and other rural areas.
The proposal also explored wider links. A connection to the Great Western Main Line was considered, and there was even early discussion about how the route could support travel to Manston Airport in Kent.
The project also raised the possibility of direct rail services from regional UK cities to Europe by linking HS2 and HS1.
But despite the potential benefits, the plan faced serious obstacles and in December 2018, the Department for Transport rejected the scheme.
Officials said it was not “financially credible without government support” and warned that building through green belt land would draw strong opposition from local communities.
The decision followed earlier choices to drop a direct connection between HS1 and HS2 in central London in 2014, and to remove an HS2 link to Heathrow in 2015.
With HS4Air ruled out as well, no alternative proposal has been brought forward.
