Sri Lanka shut down its international airport and cut power to the capital, Colombo, on Thursday, fearing an airborne attack by the Tamil Tigers.
The Tigers have already succeeded in bombing the Colombo complex
Anti-aircraft guns were fired after citizens reported seeing suspicious aircraft flying towards Colombo.
The public has been warned to be on guard after the Tigers unveiled their own "air force" with two deadly aerial bombings in the space of a month.
But the alert appears to have been a false alarm.
Two incoming Sri Lankan Airlines flights were re-directed to southern India as Colombo airport was shut during the scare.
"Passengers were ordered to the ground floor after we heard gun fire and some blasts," a woman passenger at the airport said by telephone.
"It was a panic situation, but no one was hurt."
The civilian airport uses the same runway as the adjoining military base, which was the target of the Tigers' first airborne attack last month, which killed three airmen.
A second bombing, of a northern military complex on Tuesday this week, killed six soldiers.
Analysts believe the Tigers may have as many as five light aircraft converted into rudimentary bombers, after being smuggled into the country in pieces and reassembled in secret jungle bases, says the BBC's Roland Buerk in Colombo.
About an hour after the alarm was raised on Thursday, Colombo's lights began to come back on and the airport re-opened, our correspondent reports.