> And an airport can’t be too far from a city and remain useful, since travelers need to access the city, workers need to be within commuting distance, and so on. In Canada, Mirabel airport was built 35 miles from Montreal, surrounded by a 79,000 acre buffer zone to prevent any issues of incompatible land use. Mirabel was expected to replace Dorval (today Montreal-Trudeau) as Canada’s main eastern airport, but, in part because of its long distance from the city, this never happened, and Mirabel stopped serving passenger traffic in 2004.

It was because of very stupid mismanagement and lack of connections, not the distance.

The old airport remained opened and continued serving domestic flights, while international ones were moved to Mirabel... which was extremely dumb because Montreal was the major interchange point between international arrivals and smaller locations not served directly by international flights in Canada. So most of the utility of Montreal airport was killed, and airlines started serving other airports in Canada to do the same thing.

Also, there was no good link to the airport - it shouldn't have opened without a direct at least somewhat fast rail link, but it had no good road nor rail connection.

Also, it was put in the wrong place - one of the potential locations was midway between Ottawa and Montreal and could have served both cities, but politicians decided they don't want that.