Is there a risk free way to enforce a no-fly zone over Ukraine?

Could a United Nations-mandated no-fly zone over Ukraine really work and how?

Despite pleas from the President of Ukraine, the UK and other NATO countries have continued to rule out imposing a no-fly zone over all or part of Ukraine.

Due in the most part to the fear any military intervention by NATO would anger Putin further and risk an attack on a NATO member country and ultimately throw the alliance into full conflict with Russia. 

There are, however, a small number of voices saying a no-fly zone is exactly what is needed and that it could be done with minimal risk - through a United Nations-mandated operation.

Retired Air Marshal Greg Bagwell, former RAF Commander of Operations, told Forces News if it was a UN operation it would give you a "whole different mandate".

"The general assembly, not a week ago now, voted with 141 members for Russia to leave Ukraine. That's a pretty strong mandate. 

"It's important that this is seen to be Putin against the world, not Putin against NATO which of course what he might want to play it as.

"I think that's what's spooked NATO a little bit. Therefore it's important to give it that badge of authenticity and an international flavour."

A UN-mandated no-fly zone would certainly use air assets from NATO nations and alliance members have the experience in the type of policing needed to operate a no-fly zone.

But the risk remains of NATO and Russian forces coming into direct contact, potentially triggering an Article 5 situation, where a downed NATO jet counts as an attack on all NATO countries, throwing the alliance and Russia into direct conflict. 

Watch: Why NATO aircraft are patrolling Eastern Europe's skies.

However, there could be ways around this if the political will was there.

Air Marshal Bagwell said that if it becomes a UN operation then "Article 5 isn't really at play here".

He added: "The second thing [after making it a UN operation] I would do is that I would suspend Article 5, and make I would make it clear to the Russians that I would suspend Article 5, for those aircraft participating in the no-fly zone.

"So if a miscalculation took place or even a deliberate engagement took place, we'd be pretty hacked off but it would not trigger Article 5.

"We've already done that in Syria. The operation there does have Russian and RAF aircraft flying in relatively close proximity in a third party airspace and if there was a miscalculation we wouldn't trigger Article 5."

Where could a no-fly zone be put in place?

Air Marshal Bagwell said: "You don't have to do it over the whole country.

"So you could actually have a limited one that only looked let's say at the west of Ukraine, and therefore would be purely for humanitarian reasons.

"And I think it would still need to be defended, but we're not seeing too much air activity over the west of Ukraine that I'm aware of.

"I think, that's one for example that would stay well below a threshold but if you were looking to go further - looking to go into Ukraine proper - then what might it achieve?

The former RAF Commander of Operations added: "Well, it could keep Russian aircraft out of the fight.

"That would allow a number of things - it means Russian aircraft couldn't attack anywhere in the country, or helicopters for that matter.

"It would allow the Ukrainian Air Force to operate and that's quite an important point."