A SMALL Australian-registered plane caused the 50-minute lockdown of Singapore's airspace to commercial planes on Tuesday evening (22nd January 2008).
Two Australians, the only people on board the Cessna 208 Caravan float plane - which can land on water - are now assisting in a police probe.
The security alert they caused between 7.10pm and 8pm - which led to two twin-seater F16D fighter jets being scrambled - occurred during Changi Airport's busiest period.
There are about 30 to 40 aircraft movements an hour at the airport from 7pm to midnight each day.
Aviation officials estimated yesterday that the lockdown led to thousands of dollars in fuel being lost as 16 airliners circled Singapore while awaiting permission to land.
For BI 423, an inbound Royal Brunei flight from Bandar Seri Begawan in Brunei, the situation grew serious after it ran low on fuel, and it had to land at Senai airport in Johor.
It flew to Singapore 1-3/4 hours later. Six departing flights were also delayed.
The Straits Times understands that in Tuesday's incident, the single-engine turboprop float plane began its flight from Thailand's Koh Samui island, famed for its fine beaches.
The Republic of Singapore Air Force (RSAF) Air Defence and Operations Command tracked the small plane as it flew towards Singapore, and it was quickly established that the Caravan did not have an approved flight plan - a 'red flag', especially since the Sept 11, 2001, terrorist attacks in the United States.
At 6.42pm, a pair of missile-armed F16D jets, which also have 20mm guns, thundered off from an air base.
They quickly spotted the Caravan with its massive floats - pontoons mounted beneath the fuselage - and signalled it to land at Changi Airport's central runway just before 8pm. Airport police immediately surrounded the plane.
A Straits Times check showed that the plane was bought this month by Ms Mary Cummins, who co-owns a tourist adventure flight company with Mr Rhys Thomas, a former pilot with Australian airline Ansett.
The company is based at Broome Airport in Western Australia. Ms Cummins and Mr Thomas could not be reached.
The plane, which can carry about a dozen people, had previously been flown by an airline in Koh Samui.
The Singapore Police Force said yesterday that 'two foreigners' who were in the plane are assisting with investigations.
The last time the RSAF was reported to have scrambled its jets was in August 2003 - when two Super Skyhawk warplanes intercepted a civilian plane that tried to land at Tengah Air Base.