The 1.2 million figure represents a 19% increase on September last year and means numbers have grown for 18 consecutive months.
Airport chief executive Nick Barton said: “LLA is continuing to see unprecedented demand for air travel.
“These record passenger numbers demonstrate the increasing popularity of LLA with travellers. They also highlight the importance of expanding the airport to help meet the capacity needs in the South East.”
London Luton is investing £100 million to meet the growing passenger demand and aims to increase capacity from 12 million to 18 milion by 2026.
It has appointed Whitemountain as the first construction contractor and has already opened the new enlarged security area.
Whitemountain will manage the construction and civil engineering of landside infrastructure and transport facilities. This will see the existing approach road to the terminal building become dual carriageway, the redevelopment of the short stay car parks and on-airport road network, the remodelling of the set-down area and the repositioning of the coach terminal.
The airport’s security area has been relocated to the ground floor. Alongside an investment in the latest screening technology, the result has been a significant improvement in the experience for passengers, Mr Barton said.
He added: “ The appointment of Whitemountain and the relocation of security are major strides forward in our plans to ensure we can continue both to meet growing demand in future and improve the overall passenger experience.”