This marks an increase of 3.9% compared to September 2017 and is the 20thconsecutive month that the airport has welcomed more than one million passengers.
Amsterdam, Budapest, and Bucharest were amongst the most popular destinations, as passengers took advantage of the remaining days of the summer holiday season.
The growth comes as LLA nears the end of its transformation, which has seen the airport undergo a £160 million redevelopment to increase its annual capacity to 18 million passengers per year by 2020.
As part on the transformation, LLA has doubled its retail and dining space in order to offer passengers more variety and welcomed 30 new stores, including Chanel, Oliver Bonas and Hugo Boss.
The airport has also opened a new boarding pier to accommodate new routes from its airline partners, and added additional seating throughout the terminal.
The newly-upgraded terminal is expected to be fully open by the end of the year, offering passengers greater choice and a more efficient and comfortable journey.
Nick Barton, CEO of LLA, said: “Passenger demand for air travel continues to grow, and our transformation will both help to meet this while making journeys easier, smoother and quicker.
"The opening of the terminal marks an important new chapter in our history, and the benefits will be felt by our passengers, staff and local community alike.”