Passengers using Gatwick rose by 5.1% or 131,500 to 2.7 million in March over the same month last year.
Almost 1.8 million passengers were flying on European routes, an increase of 6.1% year on year.
A large part of this growth was on flights to business destinations such as Moscow, Istanbul, Stockholm and Copenhagen, according to the airport.
There was also “significant growth” on flights to Spain, Portugal and other popular leisure destinations.
But the number of passengers flying to North Atlantic destinations slumped by 21.7%, mainly because US Airways ceased to fly from Gatwick in 2013.
This summer’s launch of Norwegian routes to the New York, Los Angeles and Fort Lauderdale should help reverse the trend of lower transatlantic traffic.
Other growth was 13.1%, mainly on leisure routes such as the Caribbean and the Canary Islands.
A number of domestic routes have seen a growth in traffic since last March – most notably flights to Newquay, which were boosted by Gatwick’s decision to waive charges on additional flights to support the southwest following the Dawlish rail line closure.
Airport chief executive Stewart Wingate said: “This has been a successful and exciting year for Gatwick that has seen steady growth, the completion of spending over £1 billion on improving the passenger experience and offering new routes that satisfy the demands of business and leisure travellers.
“These successes only add to the obvious case for expansion at Gatwick. A new runway could be delivered at Gatwick more cost effectively than at Heathrow, with significantly less environmental impact. It would also provide the connections and economic benefits the UK needs much more quickly.”