The ‘Crosswind’ runway tunnel at the airport obtained planning authorization thanks to the appeals board's ruling that there would be no unacceptably negative effects on traffic safety or the surrounding area's amenities.

The ruling supports a clearance granted by Fingal County Council in February of last year. Ryanair, the airport's largest client, and SMTW Environmental DAC, a group of citizens residing in north Dublin, challenged that decision to An Bord Pleanála.

Five “unreasonable and overly onerous” restrictions connected to the planning approval were the subject of an appeal by daa. An Bord Pleanála supported daa's grounds of appeal in each case in its verdict.

The whole alignment of the 700-meter-long twin cell enclosed underground tunnel, measured from "ramp to ramp," is 1.1 km long.

In a statement released on Wednesday, daa said it was pleased with the appeals board's decision to approve the building of a vehicle underpass in the centre of the airfield to link the West Apron and Eastern Campus.

A spokesperson for daa stated: “The tunnel is required to improve access and safety on the airfield, allowing for the segregation of aircraft and vehicles, and the movement of vehicles to the West Apron, which has been restricted since the opening of the North Runway in August, 2022.”

He continued: “Access to the West Apron is critically important to cargo operations, transit operations, general aviation, stand-by parking and contingency stands.”

“Will be critical to ensure Dublin Airport maintains safety standards and meets future operational requirements,” the statement noted.

During the building phase of the project, approximately 160 jobs will be created.

According to Mary MacMahon, who wrote a 131-page report for the appeals board inspector, the planned underpass “is a standalone, critical piece of infrastructure.”

As stated by Ms. MacMahon, the planned development is comparable to Dublin's major drainage system, where housing growth would be restricted in the absence of a suitable drainage system.

The proposal may still run into problems, though, as objectors now have eight weeks to file a judicial review of An Bord Pleanála's approval award.

The project's construction is expected to take around three years in total, with three months allocated for site mobilisation, eighteen months for cut-and-fill work, and nine months for testing and handover.

“Ryanair believes that the subway project is unnecessary because vehicular access between the eastern and western aprons of the airport is possible to achieve at surface level,” planning expert Ray Ryan of BMA Planning said in the Ryanair appeal.

According to the appeal, the unusual requirement pertaining to cross-wind situations barely impacts 0.5% of aircraft operations on a yearly basis.

According to the appeal, “this means that there will be no impediment to vehicular crossings save in exceptional circumstances.”

“The business case for the spending of over €200m on this project has not been made,” the appeal said.