A third runway at Heathrow would give Scotland access to the world's largest hub airport "on its doorstep" and double the UK's exports, business leaders have been told.

Heathrow CEO John Holland-Kaye said UK's only hub airport should be expanded over a rival bid from London Gatwick because it was the only option which would connect the UK, and Scotland, to the world and keep it competitive in the global marketplace.

Speaking today at a conference of aviation representatives in Glasgow organised by the Scottish Council for Development and Industry (SCDI), Mr Holland-Kaye said adding a third runway could double UK exports by 2020 and boost the number of long-haul destinations served by Heathrow from 80 to 120.

He said: "It would be the best connected airport in the world, and Scotland would have that right on its doorstep. We would have more capacity than Paris, Amsterdam or Frankfurt."

Mr Holland-Kaye and his counterpart at Gatwick, CEO Stewart Wingate, were making their cases to Scottish business leaders a day after the Airports Commission opened its public consultation on the airports' rival bids for expansion.

Heathrow bosses want to build a third runway while those at Gatwick want to add a second to meet growing demand for domestic and international routes, especially in rapidly growing economies such as China.

The UK Government-appointed Commission - which is also considering a third option not favoured by Heathrow bosses to extend the airport's north runway - will recommend one of the three proposals next summer.

Mr Holland-Kaye said Heathrow was already the conduit for more than a quarter of the UK's exports, including £80 million-worth of Scottish salmon and 400,000 of whisky annually, in comparison to less than 2 per cent passing through Gatwick.

However, Scotland has been increasingly squeezed out of the hub as short-haul domestic flights have made way for more lucrative long-haul routes. There are currently nine daily flights from Heathrow to Glasgow and 16 to Edinburgh, fewer than a decade ago.

"Failing to expand Heathrow would mean even fewer connections for Scotland as airlines choose long-haul over short-haul," said Mr Holland-Kaye.

He added that expansion would allow the airport to meet demand from airlines such as Air China, which have currently had to look elsewhere in Europe for landing slots.

However, Amanda McMillan, managing director of Glasgow airport - currently being purchased by Heathrow Airport Holdings' biggest shareholder, Ferrovial - said she wanted Scotland to have its own direct links with China.

She said airport bosses were already in talks about attracting a Chinese carrier to Glasgow "in the medium term".

Mr Wingate told the conference that a second runway at Gatwick would keep fares lower for Scottish passengers and better serve the growing low-cost market. He added that Gatwick already served a number of far-flung destinations such as Moscow, New York, Hanoi, Ho Chi Minh City and Jakarta but a second runway would "accelerate that growth" while offering passengers comparatively cheaper flights than Heathrow because of its foothold in the budget market with carriers such as Easyjet and Norwegian.

Mr Wingate, who started his aviation career as a customer service director at Glasgow Airport, said Gatwick bosses were also committed to keeping landing charges - the fee charged to airlines for using an airport - down. Gatwick currently charges around £9 per passenger and has vowed that if its expansion plans get the go-ahead it will absorb the cost to hold landing charges at a maximum of £15 by 2030. In comparison, Heathrow's landing charges are expected to double from around £20 per head to more than £40.

He said: "What is that going to do to ticket prices? It will be passed on to the passenger. A second runway at Gatwick will create the most competitive marketplace, and that will allow people in Scotland, the north and Northern Ireland to London and through London at the lowest cost."