Gatwick achieved a record March with 3.1 million passengers using the airport during the month.
The 5.8% year-on-year rise was helped by a 9.6% increase in long-haul passengers as the airport recorded three years of consecutive monthly growth.
North Atlantic routes were up by 19.3%, including Los Angeles (62.8%), Toronto (60.3%) and Vancouver (35.8%).
Norwegian’s new route to Boston was brought forward by two months to March due to “unprecedented” demand.
This was the first of 20 new long-haul routes planned for this summer from Gatwick including Hong Kong, Cape Town, Vancouver, Lima and Costa Rica.
European routes seeing strong growth last month included Fuerteventura (38.6%), Venice (32.8%) and Iceland (30.8%).
Gatwick chief executive, Stewart Wingate, said: “Three years of consecutive month and month growth shows Gatwick continues to provide what our passengers want – more choice and better value to a greater range of destinations.
“Our 20 new routes this summer, including Hong Kong, Cape Town, Vancouver, Lima and Costa Rica, are a resounding endorsement of the airport, from our existing carriers plus new airlines including Cathay Pacific and WestJet.”
He added: “An expanded Gatwick would build on this momentum and deliver yet more competition and choice for passengers – only last month Norwegian pledged 50 Dreamliners to a two-runway Gatwick which would transform the UK long-haul market.
“Government backing for Gatwick expansion this year will mean that the UK finally and definitively has a solution to its long enduring aviation capacity issue. Our plan is legal, affordable, cleaner and quieter and will finally deliver for Britain.”