> close all maritime corridors going through NATO territory for Russia.

Probably too extreme for maritime law. OTOH a tighter inspection regime might fly. There is a precedent in ports of call that enforce their own inspection regimes.

Profile and optionally board boats entering the Skagerrak. Registry? Condition? Incident history? Hazards of declared cargo? Too many suspicious antennas?

Full cavity search (of the ship)

"charge everyone on board with espionage, give maximum jail sentence" won't help: most of the crew has no choice in those operations, some might not even know what is going on. They also have dozens of ships that can do such damage, so no way to scare them by seizing or jailing one.

The only good way would be to close the path.

A key difference between Turkey and Finland is that Turkey has the largest army in Europe and can unilaterally take action.

Finland can only take action if backed by many other NATO members, and most especially by the US.

Dealing with this as a policing activity tells you all you need to know about the current leadership of the US and other NATO countries.

Finland has a sizable amount of hardware in storage.

And could easily donate more equipment to Ukraine.

Even if stockpiles runs low, Finland could finance equipment for Ukraine.

Both of these options would hurt Russia more, and probably cost less than direct intervention.

Or give away more explosive toys to Ukraine.

A cut cable is expensive to repair.

More toys donated to Ukraine won't just cost Russia money.

Unless the cable cutting is actually a real threat, we should suck it up, repair and donate to Ukraine.

(If an actual shooting war broke out in Europe, it's hard to tell of those cables would last long anyways)

As I recall, Russia was making a habit of cutting across Turkey's airspace and they were officially warned before the shoot-down. I may be misremembering.

> Russia violated Turkey’s airspace only once, the jet was shot down immediately, and, save to say, Putin was on the phone with Ankara to prevent an all out escalation with a NATO member that can trigger article 5 at any time for self defense after an apparent aggression. Turned out, no more airspace violations happened again.

I was on the same page as you for a long time, but aggressively defending your airspace also increases risk of collateral damage, leading to, for example, your military shooting down Azeri passenger jets. Or Malaysian ones. Or Iranian ones (to name one not committed by Russia).

>the jet was shot down immediately

By the same forces that later tried to overthrow democratically elected president of Turkey.