An empty 737 plane chartered by the Federal Government was used to transfer a single asylum seeker from Christmas Island to Perth at the weekend.
Fewer than five passengers are understood to have been on the aircraft - which usually seats 130 - including the injured asylum seeker and an accompanying Serco guard and immigration officer.
A spokesman for the Department of Immigration confirmed the Saturday morning flight and said the decision was made to use the jet to move the man because it was already sitting on standby at Christmas Island's airport.
He said it was the "quickest and best" way to get him to Perth for treatment.
The plane left for the 3-hour journey just hours before the scheduled Virgin flight to Perth departed Christmas Island that evening.
_The West Australian _ understands the man, who was on the asylum seeker boat that sank last week, was being treated for two severed fingers.
The department is understood to have then brought in a second chartered plane to the remote island to transfer 92 asylum seekers, who were not part of last week's tragedy, to Darwin yesterday morning.
Three other asylum seekers who were badly injured when their overcrowded vessel capsized on Thursday between Indonesia and Christmas Island were flown by the Royal Flying Doctor Service to Perth for treatment on Friday afternoon.
But the man transferred on the 737 could not go on that flight because he was part of a second group of 16 survivors who were brought to shore that evening.
A department spokesman said the decision to use the 737 was made on the advice of doctors, who said the man's condition was serious enough to warrant urgent transfer to Perth.
Calling the RFDS out again would have been costly, he said.
Australian authorities were yesterday dealing with the mammoth forensic, administrative and emotional toll of the tragedy, in which 90 asylum seekers are believed to have drowned.
Several of the refugees, who were fleeing the Taliban stronghold of north-west Pakistan in a bid to get to Australia, are understood to be children.
After their rescue, the 110 survivors had been housed together in one of Christmas Island's detention facilities. But authorities separated them on Sunday night into three groups that are now being kept apart - eight unaccompanied minors, 100 adult males and the two suspected Indonesian crew members.
Police said they were holding off interviewing the two suspected crew until they finished speaking to survivors about what happened.
Customs and border protection officials confirmed unused lifejackets had been recovered from the scene and would become part of the investigation into the tragedy. <div class="endnote">