"Highly unlikely" is how Minister for Health Simon Harris rated the chances of people here being able to go on summer holidays this year, a few weeks ago.

While Chief Medical Officer Dr Tony Holohan also advised people recently that they should not book summer trips abroad.

They clearly meant what they said.

Because their views were backed up yesterday by the announcement of practical measures that reinforced the Government's stated policy that people should not undertake any non-essential travel.

The decision to put in place a legal requirement for all those arriving into Ireland through an airport or port to complete a passenger locator form, coupled with the pre-existing request for them to self-isolate for a fortnight, ratchets up our border controls a step further.

It also brings them ever closer to a situation of mandatory quarantine, like that announced in the UK yesterday.

Indeed, Mr Harris did not rule out making self-isolation enforceable by law.

The measures are being implemented for good public health reasons, the Government claims, to stop the spread of Covid-19 from getting out of control once again.

You don’t have to be a virologist to see or understand the rationale.

Ireland and the UK are also not outliers in seeking to monitor those entering their territories.

For example, until July at least, those entering France will need to provide a health certificate, stating they do not have coronavirus, or they will have to opt for an alternative of 14 days' self-isolation.

It is a similar situation in Iceland and Austria. Belgium also still has a 14-day self-isolation policy.

Many other EU countries still have borders that are essentially closed to all non-essential travel.

But it is clear that plans by the aviation industry to begin a gradual return to the skies and the tourism industry to start reopening are facing serious difficulties as a result.

Ryanair intends to restore 40% of its schedule from 1 July, running 1,000 flights a day across 90% of its network.

IAG, the owner of Aer Lingus, British Airways, Iberia and Vueling, plans to run a similar number each day between July and September.

In an industry that is on its knees - and is burning through cash at the same rate as it ordinarily burns jet fuel - holding onto funding is a big consideration.

Air France KLM is being a little more cautious, operating 20% of its schedule from June, with Lufthansa doing something similar.

But with many European countries still imposing stiff conditions on those arriving into their territory, the question is: Who is going to fly abroad for a holiday, or even for work?

If you arrive in a country and have to isolate for two weeks, and then must do the same on the way back, who would voluntarily undertake such a journey?

On the face of it, the situation even appears somewhat at odds with the EU guidance published last week on a gradual coordinated opening up of restrictions across member states, so that tourism businesses can reopen and the summer season can be salvaged.

Airlines are, as you might expect, deeply unhappy with such restrictions.

Ryanair has called on both the Irish and UK governments to drop them, describing them as "unimplementable and ineffective".

It has pointed out that when passengers can use public transport to get from an airport to their final destination, what is the point of then making them self-isolate for two weeks?

The airline argues that use of face masks and social distancing should instead be sufficient to ensure the virus does not cross borders.

And it is not alone. Airlines UK, which represents the likes of British Airways, Easyjet and Virgin Atlantic, has said quarantine would completely kill air travel.

But sceptics might argue that airlines are perhaps only keen to get back in the air, because if they fly and don't cancel flights, then passengers with long-standing bookings will not be entitled to refunds.

In an industry that is on its knees - and is burning through cash at the same rate as it ordinarily burns jet fuel - holding onto funding is a big consideration.

We got a further sense of the genuine difficulties they face yesterday, with the news that Aer Lingus may unilaterally lay off staff and cut pay further after 21 June.

Cityjet is also seeking up to 700 redundancies across Europe and Ryanair is closing its Laudamotion base in Vienna, at a cost of 300 jobs.

It is an industry on its knees, looking for a way to get back up again.

Ultimately though, public health concerns will win out, for now at least.

And for airlines, a meaningful return to the skies may end up being further away than they think.