The gateway passed the milestone after setting a new record for the month of April when 1.1 million passengers (+17%) passed through its facilities.
April also marked 25 consecutive months of passenger growth at the airport.
London Luton Airport (LLA) is addressing this increased demand by investing £110million to transform the airport.
Contractors are already on site redeveloping the terminal building to increase annual capacity from 12 million to 18 million passengers by 2020.
Earlier this month plans were announced to build a £200million mass passenger transit (MPT) link to connect the rail station with the terminal.
The link will replace the existing shuttle bus and cut journey times from St Pancras to less than 30 minutes, bringing LLA closer to London than both Gatwick and Stansted.
As well as delivering major upgrades to the airport’s facilities, the transformation will also dramatically improve the passenger experience by expanding the route network.
Air Nostrum is the latest carrier to announce new services from LLA; the Spanish airline has announced that tickets are now on sale for twice-weekly flights to San Sebastián.
The new route, which will enter service on the 26 July, is exclusive to LLA and will open up access to this popular resort offering world-renowned cuisine and beautiful Blue Flag beaches.
April also saw the launch of three other new routes. Blue Air has begun flights to the historic cities of Larnaca (Cyprus) and Turin (Italy). LLA has also become the first English airport to offer a service to Paris Orly with Transavia.
Nick Barton, CEO of LLA, enthuses: “As we await a decision on a new runway in the South East, LLA continues to go from strength to strength.
"The airport is being transformed by our £110million investment, while the announcement of the new MPT link will make accessing the airport easier than ever for passengers.
"At the same time, whether you’re a holidaymaker or business passenger, our strong relationships with our airline partners are allowing us to deliver more frequent flights to a wider variety of destinations than ever before.”