Originally designed to handle 700,000 passengers, the Patna airport handled 2.11 million passengers in the year 2016-17 owing to growth in aviation during past few years.
The proposed terminal building is coming up with an investment of Rs8bn ($124m) and will have passenger handling capacity of 4.5 million. The terminal is designed to handle 2,250 passengers during peak hours.
Construction work is scheduled to start from April next year.
AAI has also decided to commence 24-hour operations at Patna airport. Operations will be starting at night from the middle of next year to reduce air traffic during the day.
Furthermore, another new terminal building is planned at Bihita with a passenger handling capacity of five million a year.
Located about 30km from Patna, this project is also estimated to cost Rs8bn ($124m).
The construction work for the terminal in Bihita is scheduled to commence in September next year, provided the identified land is handed over by the end of the month.
To reduce congestion around the terminal building and security hold area (SHA), Patna airport has constructed a temporary structure with seating capacity of 300 passengers.
Along with the temporary structure, the airport authorities introduced an additional frisking booth for security checks during peak hours.
An additional boarding gate at the airport is scheduled to become operational from February, with the expansion of the SHA on the first floor following in March.