British Airways chief executive Rod Eddington blamed the decision to close some flights at Gatwick on the airport only having one runway.
BA is cutting 3,000 jobs at Gatwick - a decision which will have far-reaching effects throughout Sussex.
The cuts are part of plans to shed 5,800 jobs worldwide and have raised fears that BA will pull out of the airport for good.
Mark Froud, policy director of Sussex Enterprise, predicted another 500 jobs would go in the county as a direct result of the BA losses, while union leaders warned BA would withdraw from Gatwick completely within two years.
Chief executive Rod Eddington recorded a special telephone message for staff explaining that the action was needed to lead BA out of a "crisis".
Mr Eddington said: "You cannot run a hub-and-spoke operation from a one-runway airport.
"The good thing for us about Heathrow is we have a true hub-and-spoke operation there.
"We can support our Heathrow services from our broader network much better than we can at Gatwick."
Opposition People living near the airport are strongly opposed to a second runway, saying the environmental impact and the need for new homes would devastate the area.
Crawley MP Laura Moffatt is one of those who has expressed stringent opposition.
But commercial leaders say it would provide a huge economic boost to the county.
Mr Froud said: "We believe there is a strong case for one more runway in the South-East.
"Businesses in Sussex would welcome it."
The 5,800 losses announced yesterday come on top of 7,200 announced in September, most caused by the downturn in air travel in the wake of the terrorist attacks in the United States.
BA plans to shrink its operation at Gatwick gradually until 2004, concentrating more on short-haul routes. The workforce will be reduced from 8,000 to 5,000.
Eight flights are being moved to Heathrow - four long-haul services this summer and four short-haul in summer 2003.
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