With the crash site in darkness, the first of many unanswered questions about the Germanwings A320 disaster in the south-eastern French Alps is what crisis caused it to suddenly descend from its cruising altitude of 38,000 feet on its way from Barcelona to Dusseldorf?

The jet had only briefly settled at that altitude when it began an eight-minute rapid and steep descent to below 11,000 feet. Without any sign of  significantly deviating from its course, it then appears to have entered a short phase of more level flight at around 6800 feet before striking the lowest part of mountainous terrain, which rose to around 9000 feet directly in its path.

The crash took 150 lives, including 16 German school students, two babies, and a mother and adult son from Victoria.

In a crisis, such as a cabin depressurisation or an outbreak of fire, pilots are trained to aviate, navigate and finally communicate.

Nothing was heard from the Germanwings jet as it dropped, as fast at one stage as around 5000 feet a minute, and it is not known if the pilots ever reached the navigate stage of their efforts to deal with the crisis of unknown cause before the jet struck the steep, mostly treeless side of the mountain with such force that parts of the shredded debris were seen at around 8800 feet.

However, most of the wreckage is lower down the barren steep slopes, in three small sections tracing a rising traverse across a set of gullies into which the rest of the wreckage and the remains of those on board have fallen.

Given the exposed, almost vegetation-free state of the crash zone, yesterday’s prompt recovery of the flight data recorder should be soon followed by the finding of the voice recorder and the eventual recovery of all of the victims and wreckage from later today.

There are all sorts of lines of questioning being followed quite reasonably in the intensive media coverage.

But to deal with some of them other than those speculating on the causes, there is nothing known that adversely reflects on the safety culture nor maintenance of Germanwings, which has been flying since 2002 as the low-cost or budget brand of its owner Lufthansa.

Germanwings had never had a fatal accident, and Lufthansa has had very few. The A320 that crashed was built for Lufthansa in 1991, and its age is not likely to be a factor because one of the consequences of being a short haul workhorse of such vintage is that by now most of it has been meticulously renewed as parts reached their limit by years or number of pressurisation cycles flown.

Which is why, paradoxically, old jets like this 24-year-old A320 are cheap to acquire but increasingly costly to maintain. Compared to the largest European low-cost carriers, Ryanair and EasyJet, Germanwings  had some much older jets in service, although there is no reputational or factual basis for believing there was anything amiss in this airline’s maintenance nor in the training and checking of its pilots.

Nor is there any statistical case for seeing Airbus A320s as less safe than other jets, including the similar-sized Boeing 737 family.  Both types are extraordinarily reliable and safe, although historically their crash records spike notably in parts of the world that are, or used to be in past decades, notably deficient in the regulation of air safety or airline standards.

It’s the where and by whom a jet is flown that ought to be top of mind for nervous fliers, not the type of jet. And this is what makes the Germanwings disaster so perplexing.

A nagging question at this early stage of the factual information vacuum in which this disaster is being reported is the lack of evidence of any change of direction by the Germanwings A320 when it suddenly dropped out of its cruise level.

That unwavering course has been interpreted as evidence that the jet was under control by the pilots. However, some expert sources have concluded otherwise, suggesting that something else was going on in the cockpit at that point. Whether the initial descent was controlled or not, the sequence of known events raises questions as to why the flight didn’t divert to the left of its generally north-east heading to avoid the Maritime Alps that were under its filed flight path.

That path would have, within minutes, taken the jet beyond those ranges to an overflight of the far higher Major Alps, where a constant heading during any crisis involving loss of height would have been manifestly more urgent and much sooner.

An early clue as to what caused the control crisis ought to become apparent if the cockpit voice recorder is found and read, as is considered likely in coming days.