Plans for a viewing balloon over Cardiff Bay face being thwarted by a man who is seeking to overturn planning permission in the appeal courts.
Kenneth Street, who lives close to the proposed location in Britannia Park, had a judicial review rejected in 2009.
Now he has won permission to challenge that ruling in the Court of Appeal.
The council said the scheme would not involve "a significant loss of open space". The firm behind the balloon now plans to erect a blimp in the bay.
Lindstrand AeroPlatforms said its tethered balloon, called the Hiflyer, would have a total height of 35m on take-off from its 32 mooring points and would rise 155m into the air, giving 30 passengers and crew in the gondola a birds eye view of Cardiff Bay, the Appeal Court heard.
It was granted planning consent by Cardiff council in March last year to station the viewing balloon in the parkland, which adjoins the picturesque Roath Basin.
In granting planning permission for the Hiflyer, the council said the scheme would not involve "a significant loss of open space" and would not impinge on already-laid-down strictures that no development would be allowed to take up more than 25% of the park, or have a footprint of more than 1,000 square metres.
However, Mr Street, backed by 80 local residents who signed a petition against the scheme, insists that that does not take into account the balloon's "outer" mooring points.
New blimp plans
Lindstrand said the balloon was only likely to be "locked down" at times when few members of the public will be using the park and when wind speeds exceed 25 knots.
Mr Street pointed out that in the Cardiff Harbour area in 2008, wind speeds exceeded 25 knots on 167 days.
Granting Mr Street permission to challenge the judicial review in the Court of Appeal, Lord Justice Sullivan said that although the case was "finely balanced" it was arguable that the council had "side-stepped" the 25% limit and its own open space policies.
No date was set for the full hearing of Mr Street's appeal, which will be before three Lords Justice of Appeal and is expected to take half a day.
Since the Hiflyer balloon was given planning consent, Lindstrand has also been granted planning permission by the council for another viewing platform - a blimp called the Skyflyer, which is due to launch in September.
It will take people in an open gondola up to 390ft (120m) above Cardiff Bay, near the Norwegian Church, for a 15-minute ride.
This scheme, however, was not subject to the legal proceedings.
A council spokesperson said planning permission was granted in March 2009 to change the use of part of the park to accommodate the Hiflyer balloon and a winch house.
Mr Street objected and he started proceedings in the High Court seeking a judicial review of the council's decision, where he was refused permission to proceed to a full hearing, the spokesperson added.
"Mr Street then applied to the Court of Appeal for permission to appeal against this refusal which has now been granted and a full hearing of the appeal will now take place. The appeal hearing will deal solely with the refusal of permission by the Administrative Court to proceed further.
"In the meantime, Lindstrand Aeroplatforms have submitted an alternative planning application for a Skyflyer tethered aerostat, viewing gondola and fixed sea platform and it was resolved to grant permission for this on April 14, 2010 subject to the completion of a legal agreement."