How can passenger plane protect themselves from incoming missiles ?

Flares are not allowed in lots of places where there is dry bush and a fire risk.

Plus it depends on the missile... I doubt they could have stopped a BUK missile or a TOR missile if they were the ones involved.

In comparison for use against modern MANPADS DIRCMS would be useful, but Pantsir or SOSNA of no use at all (nor flares or Chaff).

Chaff needs to be cut to the precise wavelength to be effective and flares designed specifically for the threat.

Very simply if fighter planes can't be safe against SAMs how could big slow airliners with poor manouver performance even have a chance.

The Russians showed the world the solution in Syria when Syrian air defence forces shot down a Russian plane... the solution is an IADS were all radars and systems on the ground and in the air combine information... a target entering the airspace is given an ID which is shared across the network so a MANPADS team is given information about all aircraft near it... if they detect something else then it is added to the system and other platforms will scan for it and try to ID it too.

A helicopter taking off in a city from the roof of a building will be detected by multiple radar who will interogate it to determine if it is friend or foe... a civilian aircraft will turn on an active signal that magnifies its radar signal so it is easy for nearby civilian and military radars to see it and to track it. A privately owned drone might not have such a signal and will need to be investigated by aircraft or radar...

While air defence platforms are deployed outside the air defence network there is a bigger risk of a mistake.

Why won't they be ineffective against BUK (I think you mean Buk M3) or TOR ?

Do you think a missile jamming system will work better than missile jamming systems on military aircraft?

If they protect civilian airliners from missile attack then the US military would start using them on all their military aircraft... which means Russian missile developers would need to work out a way to defeat those missile defence systems so they can continue to do their job of shooting down planes.

That means not only will these civilian airliners will need a huge amount of very very expensive and secret electronic equipment and systems to be fitted to every aircraft... but they will also need to continually upgrade them because a jammer fitted to an airliner could very easily be used by a modern powerful effective new missile as a signal to home in on... the jammer protecting the plane would be used by the missile to hit the plane instead...

TOR doens't need a radar lock in optical mode they can use an autotracker to follow the aircraft visually and the missile is command guided to fly to the point of aim hitting the aircraft whether it is jamming in radar or IR or any other frequency... BUK would lock on to the target with its own radar... jamming signals from the aircraft probably wouldn't break that lock but even if it did it could home in on the jamming signal as many ARH missiles have back up home on jam options.

Again, why won't they be useful against Panstir or SOSNA ?

SOSNA is a laser beam riding missile and is optically aimed. The point is that the optical system wont be detected by the DIRCMS system on the aircraft... the missile is launched but the optical seeker in the missile is in the tail and it looks back at the launcher and not at the target. That means a DIRCM (laser dazzler or jammer) on the aircraft can quickly detect and point its laser at the incoming missile (which it tracks via its IR signature from its enormous rocket plume and friction heated nosecone...) that laser can shine all over the nose of a SOSNA missile... they are solid and have nothing to do with the guidance of the missiles. The rear mounted sensor looks back at the launcher and sees a laser beam directed from the launcher and works out its position in the beam and manouvers itself into the centre of the beam which is controlled by an auto tracker to fly to and hit the target.

Pantsir does something very similar but instead of a laser beam it uses a radio link to direct the missile to manouver to centre of point of aim. The Pantsir missile has no optical port pointing towards the target that a DIRCMS could interfere with.

BTW the electronic self defence system on a modern fighter takes up space and is rather expensive and would be the main reason why suggestions that jet trainers could be used as light fighters in a real war wont work... they are generally small and light and cheap which makes them a good idea... but the cost of adding a better radar and self defence avionics means they get heavier and slower and payload is reduced and performance is reduced and of course the costs go up dramatically and it is not such a good idea any more.

It should, why not?

Well for discussions sake lets pretend each airline or civil aircraft manufacturer invests billions of dollars to develop technologies military forces spend to defend their aircraft... even if they make a major breakthrough and develop something that works surely if any airline around the world needs to get access to use them then it would be very easy for Chinese airlines and Iranian airlines and North Korean airlines and Cuban airlines and other airlines from around the world to buy these systems and fit them on their aircraft... but their national militaries might be interested to have a look too... and copy and use on their own military aircraft... once the systems are widely deployed and missiles stop shooting down aircraft in numbers except drones which wont be cheap any more if you load them up with anti missile systems of course, then the makers of missiles will need to look at those new defence systems and work out HOW TO DEFEAT THEM.

They will then upgrade all their missiles to defeat those defences so those billions spend developing the systems and the billions more spent putting them in to service just got wasted and they need to upgrade them again... more billions to upgrade more billions to install... we are talking more than the cost of the F-35 programme... trillions... but no known anti missile countermeasures can defeat SOSNA and Pantsir in optical mode and the TOR system is pretty impressive... I don't think they would be defeating that very easily either...

The best things you can do is enforce some important rules like no turning lights off in flight... and no flights without using civilian flight codes... and serious responses to countries like the US that turn off their transponders in military aircraft and sneak around doing things they shouldn't be doing, or like when US aircraft pretend to be civil aircraft when they are not.

With regard to your list I would add that Russian plane that the Ukrainians shot down on its way to Israel, and also the military but also used by civilian Il-20 Russian plane shot down by Syria.

The solution in the latter incident which was engineered by Israel to use a Russian plane as a cover for its attacks was to give the Syrian air defence force a much better view of their airspace shared by all its air defence forces... it makes accidents much less likely... but accidents will always happen.

When the USS Vincennes shot down an Iranian A300 Airbus in the late 1980s there were a lot of contributing factors and a lot of things that went wrong that could have prevented what happened... very simply Iranian speed boats (the Americans called them boghammers, but they were actually Iranian navy patrol boats) were reported as being active and a recently arrived state of the art AEGIS class cruiser... the USS Vincennes roared over into the fray to swing its new untested dick around to impress everyone about how big it is... they launched their helicopter to arrive first and see what was happening and the Iranian boats fired some warning shots to basically tell it to fuck off. The captain of the Vincennes decided that his helicopter was "under fire" and therefore he was free to use any force he thought necessary without getting permission... he had been talking with the area commander asking permission to go in and clean up those speed boats but was getting refused. There was a carrier in the area but after hearing the radio traffic from the commander of the cruiser he pulled his aircraft back because he feared this idiot might shoot them down in error... he wasn't far wrong... but having those Tomcats in the air could have solved so many problems... they could have approached the target and circled around from behind and seen it was clearly a civilian aircraft transmitting the correct civilian code on a civilian flight path... running a bit late but in the right corridor and it was also climbing rather than descending as the crew on the Vincennes claimed even though the recorded details of the incident showed it climbing to normal operational altitude with no suspicious manouvering...

The primary problem was a software and hardware design fault... a human computer interaction (HCI) fuckup.

The airbase the airbus took off from was a joint military and civilian base and as the Airbus was getting ready to take off it sqwalked its civilian ID code... the operator on the Vincennes used his mouse to move the cursor over the aircraft to check its details. The system followed the aircraft taking off with the information box following the aircraft in flight but it didn't move the cursor that highlighted the target so the cursor was still on the airfield where other aircraft were preparing to take off too including an F-14... so you start out IDing it as a civilian aircraft but after it takes off it stops sqwalking the civilian code and emits a military code because there is an F-14 sitting on the airfield waiting to take off that has powered up and is emitting its military code... so the operator sees the system tracking the airliner but is getting the information from the cursor which remains over the airfield even though on his screen it appears to be following the civil airliner... they try to contact they plane but even if they could receive military frequency messages they would ignore it because they are not an F-14 to which the messages are being directed... the F-14 on the airfield wont respond either because he is not in an F-14 approaching a US ship inside Iranian territorial waters where they chased these Iranian patrol boats too... firing 127mm shells at speed boats because those speed boats fired some warning shots with a heavy machine gun.

We all know what happens next... no response and a belief the Airbus is an F-14 and is descending flying towards the ship they try to launch a Standard missile... there is a fault and it takes 90 seconds before they launch SAMs and shoot down the aircraft...

How do we know? There was a film crew on board filming a doco and of course we got the results of the investigations too.

The point is that once that missile is launched there is often not much any aircraft can do...

It is easier to steer civilian aircraft away from testing areas, war zones, and places of high tension...

If Indians are to be believed, they shot down an F 16 last year, despite the fact that F 16s have onboard jamming system. But that could also be due to pilot error.

Even if you don't believe them Israeli F-16s have been shot down too... in fact most combat types have including a Backfire to what was probably a BUK in Georgia...

I'm just trying to find out some technological solutions.

It is a multi trillion dollar industry... good luck with that...