JAKARTA, Indonesia - The crash of a Russian-made passenger jet into the flanks of an Indonesian volcano has put a spotlight on the notoriously informal atmosphere aboard new aircraft during manufacturer demonstrations - known here as "joy flights."
These junkets for potential buyers commonly see passengers join or cancel at the last minute, wreaking havoc to manifest lists. Pilots eager to show off the versatility of their planes often make lightning-fast ascents and buzz famous landmarks.
With no sign yet of the black boxes, it is not clear what caused the Sukhoi Superjet 100 to smash into the side of Mount Salak on Wednesday, presumably killing all 45 people on board, and sending debris raining down a densely forested, jagged slope.
An investigation by a joint team of Indonesian and Russian experts is expected to take at least a year.
There is nothing to suggest the pilot did anything wrong. But the disaster is a reminder of the continuing concerns of air-safety specialists about demonstration flights. That's true not just here in Indonesia - where several invitations from Boeing, Bombardier and other manufacturers land on the desks of airline executives and industry experts every year - but globally.
Tom Ballantyne, a Sydney-based aviation expert, has gone on many such trips .
"The purpose of these flights, obviously, is to show off the aircraft to potential customers," he said.
"If they are flying over a landmark, they might circle around it so the passengers can get a better look," he said. "They might fly a little lower or show the rate of climb of the aircraft."
That's not to say they don't follow the rules, he said, or push the planes beyond what they are capable.
"But there's definitely a bit of showing off," he said.
With 240 million people and a rapidly growing middle class hungry for cheap air travel, manufactures will continue to flock to Indonesia, as evidenced by a purchase late last year by the little-known airline Lion Air.
Its order of 230 planes from Boeing Co. was the manufacturer's biggest ever, and the carrier said it will need smaller aircraft as well. Lion isn't alone. Many other Indonesian carriers, some of which don't even have websites, also are trying to build up or modernize their fleets.
The ill-fated Superjet was carrying dozens of representatives from local airlines and journalists on what was supposed to be a quick, 50-minute flight to the southern part of Java island and back. Pictures posted on social networking sties like Facebook showed excited passengers, smiling and waving in front of the twin-engine jet before takeoff. Others sipped champagne handed out in the cabin by glamorous air hostess wearing electric-blue pencil skirts, creating an unmistakable party atmosphere.
Soon after takeoff from a Jakarta airfield, however, the Russian pilot and co-pilot asked air traffic control for permission to drop from 10,000 feet to 6,000 feet (3,000 meters to 1,800 meters).
The plane disappeared from the radar immediately after - with new satellite imagery revealing heavy cloud cover and rain. It's not clear if that's why the crew asked to drop or if they got a response. Officials here say they didn't.
The pilots on demonstration flights are known to be experienced, often having spent years flying for major airlines.
Alexander Yablontsev, in charge of Wednesday's flight, was no exception, logging 10,000 hours in the Sukhoi Superjet and its prototypes.
"He was our best testing pilot, overseeing everything from the designing of the aircraft to its certification," said Mikhail Pogosian, head of United Aircraft Corporation, which built the Superjet.
Even so, at least one decision has come into question - the flight path.
"As I understand it, it was the pilot who asked to pass Mount Salak," said Ruth Simatunpang, a former investigator with the National Commission on Safety Transportation, adding that she was surprised given its infamous reputation.
The long dormant volcano has been the scene of seven crashes in the last decade, Wednesday's by far the most deadly, trailed by a 2008 Indonesian air force accident that killed 18 people.
Its jagged peaks are often shrouded in heavy mist.
"Usually, in a demo flight, you would go out of your way to avoid a route that is full of obstacles," said Simatunpang. "But almost everyone knows Salak is dangerous and that the weather is extremely unpredictable."
Like many others, she was surprised that the pilot would seek such a sharp descent so close to the 7,000-foot-high (2,100-meter-high) mountain.
"But it's much too early to say," she said. "We won't know anything until we get hold of the voice and data recorders in the black box."
Last-minute passengers switches also caused confusion, with numbers flip-flopping at least five times after the crash, while authorities tried to figure out who was aboard.
As it turned out, the final manifest was not given to officers on the ground, as is standard procedure; it was on the doomed plane.
Suharso Monoarfa, a former government minister who now has interests in the aviation industry, said he was invited on the flight, but had to cancel at the last minute.
"I was invited inside the jet to look around with my wife and son," he said. "It was exciting, the crew was very welcoming and treated us very nicely, explaining everything I needed to know."
They again asked if he wouldn't like to get on board, saying his family was more than welcome to join.
"Actually, I would have loved it, especially with my son, but it was a 50-minute joy flight, and that was just too long. I had a meeting to get to," he said.
He said he was horrified when he heard what had happened.
"My heart was pounding when I heard the plane had lost contact," he said. "It's unbelievable. How could such a sophisticated plane go missing and crash?"
Ballantyne, the aviation expert, said pilots on demo flights often do things that a normal scheduled airline service would not.
But, he said, they do have to contact air traffic control to ask for permission - as the pilots of the Superjet did - before making any such maneuver, and they would descend only within acceptable rates of the aircraft.
"You wouldn't expect him to do anything out of the envelope, even with customers as passengers aboard."
Associated Press writer Niniek Karmini contributed to this report.