Air travel to and from Montreal has come a long way in recent years, but one of the local airport authority’s key projects is stuck at the departure gate.

In 2004, after years of debate, Ottawa gave up on Mirabel Airport, a white elephant that never lived up to the grandiose dream of becoming Canada’s eastern aviation hub.

Six years ago, all passenger flights were consolidated back at Dorval. Renamed Pierre Elliott Trudeau International Airport, the formerly rundown airport, just 20 kilometres west of downtown, is shiny and efficient today — thanks to $1.5 billion invested over the past decade by Aéroports de Montréal, the private, non-profit airport authority.

Trudeau Airport now has a massive new international arrivals complex, inaugurated in 2004, and an impressive, $300-million U.S. departures area that opened in August 2009. In the basement of the latter is the shell of a railway station that will zip passengers between downtown and the airport. Some day. Maybe.

For the past five years, the airport authority and the provincial agency that runs commuter trains in the Montreal region had been working on a joint plan to create a downtown/airport shuttle while also improving the paltry commuter service between downtown and Montreal’s West Island and the off-island suburbs west of Trudeau Airport.

But in May, just before that plan’s final study was to be tabled, Aéroports de Mon-tréal announced it was going it alone with a train that would run non-stop between the airport and downtown Montreal’s Central Station. The airport declared that efforts to expand commuter service were fruitless.

The airport’s $600-million proposal, with trains running every 20 minutes most of the day, will require $200 million each from Ottawa and Quebec, with the rest coming from private partners. It would carry 2.4 million riders in its first year, the airport says. This plan is backed by the City of Montreal and the Board of Trade of Metropolitan Montreal.

On the other side is the Agence métropolitaine de transport, which has its own plan, in conjunction with real estate developer Cadillac Fairview Corp. Ltd. Under this plan, more than $1 billion would be spent on both an airport train and significant improvements in commuter service. It involves building a new intermodal transit hub downtown, next to historic Windsor Station.

Cadillac Fairview has spent $150 million on property in the area, with the intention of building a major, multi-use development similar to its Maple Leaf Square project in Toronto. This Montreal project, including the transit hub linked to Windsor Station, would help extend downtown Montreal into a now-derelict neighbourhood.

The location of the downtown station is the key point of disagreement between the airport and transit authorities. The airport says Windsor Station is too far from hotels and office towers for tourists and business travellers. The transit authority says it’s only a few blocks from Central Station.

Another hurdle for the transit authority is the fear that a viaduct to get trains around the Bell Centre would be a monstrosity. Stuck in the middle are local commuters.

Thirty-one suburban mayors and several local economic development agencies have backed the commuters and the transit authority. They argue that if Ottawa and Quebec have $400 million for new trains, they should help Montrealers heading to work and to school — not tourists and business travellers.

Some mayors are now calling for a scaled-down version of the transit authority’s plan. Instead of building an expensive eyesore to get around the Bell Centre, they say, spend a lot less and build a station before the suggested detour around the arena.

Meanwhile, the airport authority’s contention that access to Trudeau Airport is poor is becoming less and less true. Quebec is spending $100 million on a highway overhaul that will include a new airport connection to the highway that connects the airport to downtown. And Montreal’s transit agency has started a new airport bus shuttle (the 747), with nine downtown stops.

As the two authorities bicker, the ones holding the purse strings, Quebec and Ottawa, have been mum, not taking sides. When will the train leave the station? For now, the departure board says: Delayed.

IE