As the last commercial flight for the day left for neighbouring India, the authorities closed the check-in counters and the only runway at the Bandaranaike International Airport, officials said.
"Aeroplanes will not be able to come in or take off, but all other aspects will be fully functional," Sri Lanka's civil aviation chief Prakrama Dissanayake told AFP.
He said air traffic controllers would remain at their posts in case of any emergencies, including planes in the region which may want to make an emergency landing in Sri Lanka.
He said a large number of Sri Lankans who were due to take flights when the airport reopens early Friday were already camping at the airport lobby.
"Passengers who are coming from the provinces are sleeping in the corridors," a spokesman at the airport said.
"They are staying overnight for a flight to the Middle East tomorrow morning."
The authorities feared that the Tiger rebels who are fighting for an independent Tamil homeland could use the c