Work has begun on a new rail link to Cardiff International Airport.
Nearly 2m passengers travel through Cardiff airport every year
The £6m scheme will enable people from as far as Birmingham and Swindon to use the airport in Rhoose, Vale of Glamorgan.
The track will be completed next year and it is believed direct services from London Paddington are being considered.
Rail passengers' spokesman Clive Williams said: "A European capital city needs these modern transport interfaces."
There is currently no rail link to Cardiff International Airport, Wales' largest, with public transport provided by bus services.
Clive Williams, of the Rail Users' Passengers' Committee, said the plans would help revive rail transport in the Vale of Glamorgan, as well as allowing Cardiff Airport to compete with other regional airports.
"It's very significant indeed - I think today's a real red letter day," he said.
"We have a government that's committed to integrated transport and the Welsh Assembly Government is committed and here we have the opportunity for people to be able to travel to Cardiff International Airport by rail."
Asked on BBC Radio Wales if main-line Inter City services could use the new airport station, Mr Williams said: "We've had success with the introduction of half-hourly services between London Paddington and Cardiff.
"There is this possibility to look imaginatively at the prospect of some Great Western services coming to Rhoose, so people at Swindon or Bristol Parkway can travel to Cardiff Airport."
He added that the rail link provided the potential for airport passengers to travel from as far afield as Birmingham and would allow Cardiff to compete with other regional airports.
Two new stations will be built along the Barry to Bridgend route, which currently carries freight, with work starting on them by the spring of next year.