The fire was detected at 5.40 PM at the Changi Airport Terminal 2's air conditioning equipment room and the smoke started entering the departure hall.
Though the fire was quickly put out, its fallout stretched late into the night.
"In this day and age of heightened security alerts, nothing is too small to neglect or downplay," aviation analyst Shukor Yusof of Endau Analytics was quoted as saying by The Straits Times.
About 40 flights and thousands of travellers were affected by the fire, said the Changi Airport Group. In several cases, the delays stretched to three hours or beyond.
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"It is highly unusual for any incident to occur at Changi, so when something does happen, you would expect that they would take extra precautions to ensure everything is in order," Shukor added.
Ramanathan Mohandas, head of the diploma programme in aviation management at Republic Polytechnic here, said every fire that breaks out at any airport must be dealt with seriously.
"A full clean-up needs to be done and systems and processes checked to make sure everything is working properly before the terminal reopens," he added.
No point rushing to resume services and risk something else going wrong, which would be even more irritating for passengers, he said.
Two airport staff were taken to hospital for observation and another four were treated at a clinic in Terminal 3.
The Singapore Civil Defence Force gave all-clear for the terminal at about 10 PM, and the operations were resumed progressively.
Changi Airport handles 60 million passengers a year.
Terminal 2 serves mainly Singapore Airlines' regional flights as well as SilkAir and TigerAir, which flies to India as well.