Unauthorised drone flying has prompted disruptions at Singapore's Changi Airport for the second time in a week.
The country's Civil Aviation Authority said 18 flights had been delayed, and seven flights diverted due to drones and bad weather.
Last week, one runway was suspended at Changi and dozens of flights delayed after drone sightings.
Airports around the world face growing security concerns as drone use becomes more common.
In a statement on Tuesday, CAAS said: "15 departures and 3 arrivals were delayed and 7 flights were diverted due to bad weather and unauthorised drone activities".
"Members of the public are reminded that the authorities take a serious view of errant operations of unmanned aircraft which may pose threats to aviation or endanger the personal safety of others," the statement said.
The agency said investigations are "ongoing".
CAAS also said offenders could face fines of up to $20,000 Singapore dollars ($14,780; £11,596) or 12 months in prison.
It marked the second time in a week that flights at the Singapore airport - a major international transit hub - had been disrupted by drone activity.
Last Wednesday, CASS said 37 flights were delayed and one flight was diverted after "confirmed sightings of drone flying in the vicinity of Changi Airport".