It seems that the russians have effectively no air defence detection capability accross Russia and they could not detect a C172 sized aircraft.

Now imagine if the Ukrainians could take a few clapped out airliners that were heading for the scrap yard. A 737 sized airframe could easily carry 10 tons of explosives and 50,000lbs of fuel. Now that would make one helova mess it it plowed into an oil refinery. Surely 5 or 6 barely airworthy airframes could be scrapped up around the world for one final flight.

and crew those with al-qaeda ISIS supporters, maybe?

Putin might look inside his fireworks bag and select one of the large ones he has kept for the finale.
(As long as they are not damp.)

Remote control and autopilot work as well for airliners as for smaller aircraft - in fact even better because, once airborne, they already have a built in autopilot...

Here's one they did years ago.....

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What do you base this on ? Nothing has changed AFAIK except they are building a railway whucich is certainly not complete .

Trying to fly a big aircraft by remote is problematic due to the size. Lag is the problem which is why the above aircraft missed it's marks. The crash was a fail as were other remote airliner style crashes.
Small aircraft are more nimble and can be placed on target a lot easier. Also r/c is not drone tech. Drones are autonomous.

Regardles of the technical challenges, I think part of the problem with a potential 7-drone-7 would be the PR fallout from mis-targetting. At the moment Russia, and to a lesser extent Ukraine, are suffering a percentage of missiles/artillery/bombs which are striking civiian buildings, whether due to inadequate care in targetting, deliberate intent, or premature encounters with air-defences.

However tragic the consequences for civilians receiving an unexpected Kinzhal, the outrage rarely persists in public consciousness beyond a day or 2. The image of a flak-damaged, explosive-laden, airliner flying into a high-rise however is going to remain like, well, you know .....

I am not suggesting they should not take down the bridge, but that it may end up being more of a symbolic act, and a personal affront to Mr P.
The Russians know that destroyed railway lines can be more quickly repaired on solid land as opposed to on a bridge, which is why they are pressing ahead with the rail network throughout their newly-established land bridge joining mother Russia through Mariupol, around the Azov Sea to Crimea.

I am querying the land-bridge that you say they have. Yes, they do - and have had for most of the war - have a continuous strip of land between Rostov and Crimea, but this is just land and not the "land-bridge" which is referred toin reports. This would be a major supply route like a major rail or road -link outside of bombardment range and these links do not exist.

There is also a bigger issue here. If Ukraine is resorting to using surplus civil aircraft as missiles it's running out of missiles.

My guess is that the orcs tried to steal the bricks and the roof sheets of some garden shed. Garden shed for I can't see no toilet seat inside.

Zelenskyy: "Russia is planning to mobilize additional 300k troops by June 1st"

How it started: "we have 190k men and we'll take Kyiv in three days"
How it's going: "we are on our third mobilization wave with yet another 300k men to make up for the already lost 450k troops on our third year of war and aren't any closer to Kyiv than on day 1"

Do you mean this fireworks cracker?

"Despite months of preparations and training, it seems that the western-supplied F-16 fighter jets due to arrive in Ukraine in July may be ‘no longer relevant’ in the fight against Russia. Speaking on condition of anonymity to Politico, a senior Ukrainian military official dismissed the impact that the aircraft would now have on the war effort. ‘Often, we just don’t get the weapons systems at the time we need them – they come when they’re no longer relevant,’ the high-ranking official said. ‘Every weapon has its own right time. F-16s were needed in 2023; they won’t be right for 2024.’Volodymyr Zelensky first campaigned for the West to supply his country with the US-made aircraft in the summer of 2022. In what has become a regular refrain among Kyiv’s western allies, the request caused many months of hand-wringing and infighting, notably in Germany, where politicians feared that supplying the jets could lead to an escalation in the conflict. In the end, however, around 60 F-16s were pledged by Nato members, but with training timelines adding to the delays caused by the West’s initial hesitation, which is why the first aircraft will only be delivered to Ukraine this summer.
Now reliant on sourcing weapons from Iran and North Korea, as well as dipping into supplies left over from the Cold War, Russia has consistently, but successfully, been forced to play catch up to match the western weaponry Kyiv is using. As such, the Ukrainians fear that the jets may no longer be effective as Moscow has the capability to counter them. Instead, the official said what Ukraine needs are more traditional weapons and drones: ‘We need Howitzers and shells, hundreds of thousands of shells and rockets.
Russia is expected to mount a major push in the coming months ahead of a summer offensive, after a recent surge in missile and drone strikes that have targeted Ukraine’s infrastructure. Among the weapons Ukraine wants are long-range Taurus missiles, capable of striking targets 310 miles away. With the West yet to make a conclusive decision on whether to send them, Ukraine may once again find itself in a race against the clock." [Spectator today]

All that Tutor time (taken from UASs I believe) in vain?

A couple of unsubstantiated leaps too far I would say.

Ukraine has no missiles capable of 1 200 km , so they obviously can't run out of them. Most likely is they were able to convert this craft to carry extra fuel for the distance and then add whatever weight of explosives was still possible.

Now that brings some memories back.

https://en.wikipedia.org/wiki/Mathias_Rust

While their AD seemingly can't detect small light aircraft (as also proved all those years ago with the Mathias Rust flight) its highly likely it would be able to detect an airliner, especially given need for civil ATC etc.

This talk of airliners being used as missiles is a little like Hitler and his Wunderwaffe.
There is no need to re-invent the modern battlefield - drones are doing that with aplomb.
What Ukraine needs is for the US to sort out its Congress nonsense and provide Bradleys, MLRS, F16s, Support Helicopters and more shells than can be fit into 10 Super Container Ships.
Its all there sitting in the desert anyway.
Mix in a few dozen Taurus missiles and the expected Russian Offensive will be a dampened to a stalemate again.
If the massing of mines worked for the Russians, I hope the Ukrainians have the same response to a Russian sojourn this summer.

Using large aircraft was tried out in WW2. It didn’t work then and killed a possible future US president, Joe P. Kennedy.

https://en.wikipedia.org/wiki/Operation_Aphrodite

Taking events and technology of 80 years ago and using it as a predictor for current situations ( as I think you are suggesting ) doesn't seem very valid to me.