IT NEEDS to be said again and again - Dublin Airport is a mess. And though the new Pier C, with its cool grey interior and aeronautical allusions, represents an improvement on most of the rest of it, there can be no escaping the grim conclusion that Aer Rianta, in its overall approach to the airport's development, seems to be making it up as it goes along.

In that sense, Dublin Airport is a metaphor for Ireland itself, offering first-time visitors an instructive, if unintended, introduction to us as a people. It is, after all, the first port of call for most foreigners; that we should have done nothing to protest against its chaotic development tells them nearly all they need to know about the value we assign to good architecture and design.

Architectural standards at the airport have plummeted since the completion in 1940 of the original terminal building, long recognised as an outstanding and even romantic work of modern architecture. Yet Aer Rianta has never, ever, had any of its plans rejected by the planning authorities; as master of Dublin's most important economic zone, it always got what it wanted.

The airport authority's unbroken record was confirmed again by An Bord Pleanala's recent decision to grant planning permission for a new pier projecting more than 200 metres from the northern end of the original terminal building, subject to an astonishingly small number of conditions - two, in all - and even these ignore the central question about the pier's visual impact.

This issue had been raised by Catherine FitzGerald, a Limerick-based architect and grand-daughter of Desmond FitzGerald, onetime professor of architecture at UCD and head of the team that designed the original building. In defence of her grandfather's greatest work, she appealed against Fingal County Council's decision last April to grant permission subject to just four conditions.

No attempt was made to amend the design in any way, either by the county council or the appeals board; people building bungalows in north Co Dublin have had to comply with more conditions. The paltry number of conditions laid down for this major public project is truly astonishing and provides a real indication of the virtual carte blanche given to those who run Dublin Airport.

What else can one make of the fact that An Bord Pleanala reduced the number of conditions to two, saying it was satisfied that the design would "integrate functionally with existing development at the airport (and) would not seriously injure the visual integrity of the airside of the old terminal building"?

Bizarrely, neither of the two conditions imposed relate to the design of Pier D.

In its two-page decision to grant permission - surely one of the shortest ever issued for such a large project - what the appeals board said it was "having regard to" in approving the project was "the established use of Dublin Airport, the recent and projected growth in air traffic at the airport and the need to provide adequate facilities to meet this growth".

So the airport has become such a Goliath that the planning authorities cannot bring themselves to reject expansion plans, lest this hold up plans to cope with ever-increasing passenger numbers. Yet in this case, what An Bord Pleanala could have done was to follow the advice of its senior planning inspector, Stephen Dowds, who trenchantly argued that permission should be refused.

In his 15-page report on the appeal, he said he had "no doubt that the proposed Pier D will substantially detract from the setting and environs" of the original terminal building. Furthermore, he agreed that it would add to the aesthetic "morass" of buildings at the airport with their "unsatisfactory mix of different styles, confusing layout, crude proportions and poor finish(es)".

Mr Dowds also criticised the external finish of Pier D, described in the planning application as "a solid/glazed curtain walling and cladding system constructed of aluminium alloy framing sections and aluminium alloy sheet or similar approved." It had been designed to "the highest architectural standards" with "meticulous attention to detail", according to Aer Rianta.

This was not the inspector's view. "The entire external appearance gives the impression of enclosing the maximum area at the minimum cost, rather than the claimed careful attention to detail which would create a structure sympathetic to the original building", his report says. The scale, design and layout of Pier D - as well as its cladding - would be "quite unsympathetic".

Mr Dowds pointed out that the old terminal is a List 1 building, one of the few Modern Movement buildings in Ireland with such exalted status, and that the Fingal county plan specifies a need for special control of developments affecting listed structures. However, the file shows that the Fingal county architect, David O'Connor, was not even consulted.

Neither was Duchas, the State heritage service, despite its insistence that there was a statutory requirement to do so. In a submission to An Bord Pleanala, it said the plans submitted by Aer Rianta were "inadequate" to assess Pier D's impact. However, it said an addition of the scale proposed "could not possibly be conceived to have no negative impact on the existing building".

Aer Rianta's response was to argue that, since there is no public access to the airside of the old terminal, its landward side is therefore more important - and this view of it would remain available. But Mr Dowds said it "cannot be contended that one side is the major elevation and the other is a hidden rear" - especially as the airside is still seen by anyone who gets on or off a plane. It is this airside view of the old terminal that will be compromised by Pier D. "The one good view of this elevation is from the north-west and the new pier will protrude out in exactly that direction", he said. In particular, its cantilevered, semicircular flying decks at either end "will be lost from sight", according to the inspector.

He openly confesses his fondness for the old terminal, which won the RIAI Triennial Gold Medal in 1943. Like so many others, he had been familiar with the building since childhood, when it symbolised the romance of air travel. Now, inspecting it in the context of the planning appeal, he was struck by "the particularly fine quality" of the structure.

However, its symmetrical form is nowhere acknowledged in the Pier D plans, drawn up by Aer Rianta Technical Consultants, an in-house team. For a start, it does not match Pier A - the 1960s projection from the southern side of the old terminal - in terms of height, length, width or overall design. It is also "splayed awkwardly", as Mr Dowds noted, to avoid disrupting a nearby hangar.

The inspector accepted that Aer Rianta had the "extremely difficult task of coping with the spectacular growth of air traffic". However, he recommended that permission should be refused for Pier D because it would "seriously detract from the setting" of the old terminal building and would "seriously obscure" the remaining uninterrupted view of its airside elevation.

Had An Bord Pleanala upheld the inspector's view, it would not have been the first time that it acted to defend an important modern building. Three years ago, it refused planning permission for a scheme which would have altered the appearance of the unlisted Carroll's Building on the Grand Canal, dating from the mid-1960s. The case for doing so at Dublin Airport was much more compelling.

During the course of Ms Fitzgerald's appeal, Aer Rianta blithely responded to criticism of the absence of any master plan for the airport by saying there was no statutory requirement to produce such a plan and, in any case, it would be "premature" pending transfer to the authority of ownership of the airport under the 1998 Air Navigation and Transport Act.

Aer Rianta could, of course, get the best architectural advice by holding a major design competition for Dublin Airport - not to tart it up superficially, but to tackle its basic defects and chart a new, more coherent direction. However, the principal architectural competition Aer Rianta seems to be interested in is fee-bidding; those who tender the lowest fee get the job.

An Bord Pleanala taught the National Gallery a lesson when it shocked everyone last year by rejecting the gallery's original plans for Clare Street; but then, the gallery is merely a national cultural institution. Dublin Airport, on the other hand, is crucial to "Ireland Inc", so we are all supposed to turn a blind eye and pretend that it is not turning into something like a dog's dinner. No amount of colourful art festivals can disguise this essential fact.