Gatwick says it can handle 11 million more passengers a year by 2030 without needing a second runway.
The airport's publishing plans for its future later today.
Gatwick currently handles around 34 million passengers a year but says it could handle up to 45 million. One of their aims is to get more people to travel to the Sussex terminals by train.
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Holly has Tuesday's forecast for the east of the region.
Holly has Tuesday's forecast for the west of the region.
The proposal will see the introduction of a discounted railcard for 26-30-year-olds, as the government looks to lessen the cost of living.