The Scottish Council for Development and Industry (SCDI) has also made the case for action to be taken to increase long-haul services from Scottish airports by reducing air passenger duty.
The SCDI has responded to a consultation on the UK's existing airport capacity launched by the Airports Commission, which is examining the need for additional UK airport capacity and will recommend to the government how this can be met.
It is currently consulting on the connectivity provided by regional airports and airports other than Heathrow and Gatwick serving London and the south-east of England.
The SCDI's director of policy Gareth Williams said: "Air access through a UK hub in London is of strategic importance to the Scotland economy. It is vital that we halt the deterioration of our air connections and we secure for the long-term frequent services from our city-regions to support the economic growth of our industries."
Mr Williams said the SCDI had held discussions with commission chairman Sir Howard Davies, and was heartened that he seemed to understand the importance of Scotland's connectivity to and through London.
He added: "We hope that the commission will ensure that new capacity serves the whole of the UK. Scotland's major airports are showing growth again and the success of the Commonwealth Games provides a great opportunity to stimulate global interest in tourism and business tourism in Scotland. We therefore want the airports to be able to attract as many direct international routes as possible."
In response to the commission's question about key barriers for new services at regional airports, he said: "It is clear that the impact of the highly uncompetitive level of air passenger duty must be addressed."