Boris Johnson has said he wants to cut air passenger duty on domestic flights in a bid to boost travel connections across the UK.
A consultation will examine options including creating a new lower domestic rate or exempting return flights.
The move is likely to be welcomed by struggling airline operators hit by Covid, but worry environmental groups.
The PM has also committed £20m for rail and road links and a review of a bridge between Northern Ireland and Scotland.
Mr Johnson has pledged new funding to upgrade road, rail and sea connections across the UK in an effort to reduce delays and bottlenecks and stimulate economic growth.
Writing in the Daily Telegraph, Mr Johnson said a lack of a UK-wide transport strategy had led to “inadequate connections” between the four UK nations.
“For far too long, we have tended to carve up the country through a devolve and forget approach,” he wrote.
Mr Johnson has championed the idea of connecting Northern Ireland with the British mainland via a bridge, despite scepticism from the Northern Irish and Scottish governments.
Two routes, between Portpatrick and Larne and Campbeltown and the Antrim coast, have been proposed.
Announcing the findings of an interim report into transport connectivity by Sir Peter Hendy, the PM confirmed a separate feasibility study into the idea.
Two engineering professors will assess an outline cost and timescale and the associated works needed.
Architect Prof Alan Dunlop, who has long backed the idea of a bridge from Northern Ireland and Scotland, said he was confident the project was feasible.
“There are geological and infrastructural challenges, I don’t deny that,” he told BBC Radio 4’s Today programme.
“But I’m absolutely convinced – and I’ve been looking at this now, researching it quite solidly, for three years – that the UK has both the engineering and architectural talent.”