An official feasibility study is to assess the possibility of building a bridge or tunnel between Northern Ireland and Scotland.
The transport expert Sir Peter Hendy was asked by the government to examine connections between the different parts of the UK.
He has said further work should now be undertaken to look at a "fixed link" across the Irish Sea.
Two engineering professors will assess the potential project.
They will look at the feasibility of such a link, an outline cost and timescale and the associated works needed.
They are Douglas Oakervee, a former chairman of HS2 and Crossrail, and Gordon Masterson, a former vice-president of Jacobs Engineering.
'£20bn a conservative estimate'
Plans for some kind of link between Northern Ireland and Scotland go back as far as the 1890s.
The Democratic Unionist Party (DUP) revived the idea in its 2015 general election manifesto and Prime Minister Boris Johnson has previously described a bridge as a "very interesting idea".
Some experts have suggested £15bn might be required for the project but others have said that £20bn would be a conservative estimate.
In a submission to Sir Peter's review, a rail industry body, the High Speed Rail Group, proposed tunnelling under the Irish Sea between Stranraer and Larne.
The prime minister has said the Hendy review delivers on ambitions for "a UK-wide transport network that encompasses sea, rail, and road".
But Stormont's Infrastructure Minister Nichola Mallon said the review "represents a gross breach of trust and is all about meeting Tory manifesto pledges".
She said she had engaged in good faith but the review is "about concentrating power in Whitehall and detaching decisions from local ministers".
She told BBC's Good Morning Ulster programme she believed it was about "London being able to impose its decisions" on NI.
She said Westminster was "obsessed with centralising spending powers in devolved matters".
The pipe dream bridge between the North and Scotland is a smokescreen for the Brexit fallout amongst the unionists who engineered it on both sides of the Irish Sea.— Michelle O’Neill (@moneillsf) March 10, 2021
Sinn Féin Deputy Leader Michelle O'Neill said it was a "pipe dream bridge" and a "smokescreen for the Brexit fallout".
SDLP leader Colum Eastwood said it was a "fantasy bridge" when roads and rail networks had been "decimated from decades of underinvestment".
Speaking in the House of Commons on Wednesday, the Foyle MP asked the prime minister: "What mandate does he think he has to override the democratically elected people of Northern Ireland to impose a bridge that goes through miles of unexploded munitions and radioactive waste?"
Boris Johnson replied that the review would be of "massive benefit to NI".
He said the SDLP leader should appreciate it and he was "amazed by his negativity".
'Stop politicising the matter'
The DUP's transport spokesman in Westminster, South Antrim MP Paul Girvan, said the project was being "rightly spearheaded by London as it is taking an overarching view of UK infrastructure rather than each devolved region working in a silo."
He said Ms Mallon should "stop politicising the matter, lift her eyes, look to the future and ensure there is better infrastructure for the next generations."
"Progress on removing the burden of Air Passenger Duty on our flights and improving Scotland's A75 should be welcomed by NI travellers but it is disappointing that our transport minister is taking such a narrow nationalist outlook.
"We want to see APD abolished and a long-term UK wide recovery plan put in place for the aviation sector which has been hit so badly by Covid-19."
UK Transport Secretary Grant Shapps said the purpose of the review was to "make it easier to get around the whole of the British isles" and that it would include north-south connections as well.
"If we do this it benefits everyone as it makes it easier to get goods in and out of NI," he told Good Morning Ulster.
He said there should be "nothing controversial" about a tunnel between NI and GB.
In response to finance concerns, when money is needed for New Decade New Approach commitments, he said costing would be explored in the study.
Road upgrades proposed
The APD and A75 proposals are among the review's more prosaic recommendations for improving connections between Northern Ireland and the rest of the UK.
An upgrade of the A75 would mean improving the main road between the port of Cairnryan and the M6 motorway in Scotland
Much of Northern Ireland's freight shipments arrive by ferry into Cairnryan but then face a journey of 100 miles (161km) along the A75, a mainly single carriageway road, before they can join a motorway.
Improving the A75 is one of the projects which will share £20m of development funding.
The government has also announced that a consultation on aviation tax reform, announced at Budget 2020, will be published shortly.
The consultation will include options to change the air passenger duty (APD) treatment for domestic flights.
APD is a tax levied on air passengers, which varies according to destination and class of travel.
The prime minister said he wanted to see it cut on domestic flights.
The DUP and Northern Ireland's airports have long called for APD to be cut or abolished on domestic flights.
Aviation groups have welcomed the prospect that APD could be cut but environmentalists have reacted with dismay.
'Naked power grab'
Scotland's Transport Secretary Michael Matheson said the report is "very weak and doesn't really tell us anything new."
He added the review was set up without consulting the devolved nations and amounted to a "naked power grab".
Mr Matheson told BBC Radio's Good Morning Scotland programme: "It is nothing more than a vanity project for Boris Johnson."