For David Crombie, the fight against jets at the island airport is reminiscent of the battle to stop the Spadina Expressway.

The former mayor seems to weigh his words carefully, thinking back to the 1960s-era fight against a planned highway that would have cut through the downtown, when asked about the parallels.

"The Spadina Expressway put a mirror to us to say: 'Was this what kind of city you want?'" the jet opponent finally said. "[Island expansion] is not quite there but it's damn close because … there's no doubt that it will change the nature of the waterfront. So, yes, it's a kind of identification question."

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The issue – which is coming to a head at city council – is increasingly being characterized as an existential debate for the city: Proponents say that allowing jets to fly off the island will help Toronto compete on the world stage, while opponents argue it will undermine a generation of work to revitalize the waterfront.

The debate over expanding the island airport goes to executive committee on Tuesday, with a full council meeting coming the following week.

On the table is a formal city staff recommendation to approve preliminary negotiations, under strict conditions, that provide a way to move past the current ban on jets. But waiting in the wings is a contrary proposal to lock the ban into place.

Both sides of the debate have been ratcheting up pressure, dangling ads in front of politicians and the public and touting growing lists of endorsements to their cause.

Among the biggest names to have gone on the record for expansion is urbanist Richard Florida, who says that the airport can be a crucial hub allowing the flow of people and ideas between Toronto and other major cities. A prominent opponent, the artist Edward Burtynsky, who has photographed man-made environmental damage around the world, counters that the risk to the waterfront is too great.

Is it really this binary, though? Is there not a compromise that will satisfy people who care about both the economy and livability along the lake?

The Toronto Port Authority (TPA), a so-called government business enterprise that owns and operates the airport, says there is. It has offered an interim cap on passengers and a moratorium on future changes, to see how a shift to jets is working.

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The city staff report recommending negotiations also points to a middle-ground approach, suggesting a phased series of talks that would bring a vote on jets to council only after a series of issues has been addressed.

But opponents say that it was a compromise in the first place to allow Porter Airlines to fly its current fleet of turbo-props from the island. They worry that extending the runway by 400 metres for CS100 jets opens the door to airport growth that can't be constrained by rules that could always be changed later.

Ahead of the council debate, The Globe looks into what's at stake.

How busy will it be?

At present, there is an effective limit of 202 commercial slots – an industry term meaning aircraft takeoffs or landings – in a day.

This is a mathematical limit based on the total allowable restriction on noise, which includes noise that's produced by medevac and general aviation flights. It means that the number of commercial slots could rise if these other types of flights were to decline, provided the overall noise limit is not breached.

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At the heart of this week's city staff report is a commitment to stopping further growth in commercial flights. The report's recommendations, which would form the basis for talks that could lead to jets, insist that the process must be preceded by a pledge limiting the number of flights to the current cap of 202.

That represents a change from the current rules, which are based on a calculation of the noise generated by the airport. The TPA would not comment on the city's position after the report was released, but this runs contrary to its previously stated stance.

On a recent visit to The Globe and Mail's editorial board, TPA chair Mark McQueen rejected a limit on slots. "The airport's already restricted and everyone agrees on what that is. What is wrong with the current restriction?"

The report also calls for caps on passenger volumes that are considerably lower than what the TPA has offered.

Roughly 2.3 million people used the airport last year, about two million of them local passengers and the rest connecting through. Passenger volumes theoretically could rise to 3.8 million under the current situation but growth is ultimately limited by infrastructure and the number of people who can fit on a plane.

The TPA has offered an interim voluntary cap of about three million local passengers through an expanded airport until traffic issues are addressed.

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Mr. McQueen is dismissive of what he called "speculating" on future technology that could lead to bigger planes able to meet the noise requirements. "As with a real Battlestar Galactica, that aircraft you refer to is not currently on any manufacturer's drawing board," he told a reporter on Twitter.

The city report cuts through the debate with simple limits. It would require a pledge not to exceed 2.4 million local passengers during the talks and would cap that figure at 2.7 million if and when jets are approved. Only later, based on still more negotiation that would include local transit improvements, might that limit be revised upward.

Deputy City Manager John Livey said that the caps are restrictive even though they are considerably higher than the current passenger volumes, noting to reporters that Porter has had very rapid growth.

The local impact

Advocates of expansion say that the change will be more evolutionary than revolutionary and shouldn't cause a meaningful difference to the experience of boaters, pedestrians and residents. Gautam Malkani, of the citizens coalition No Jets TO, counters that the plan raises the question of "how big can this airport get before we pass the tipping point – we think we're at the tipping point."

Buoys, lights and blast walls stand out as particular points of contention – and the city report offers some solace on these to the anti-jet faction.

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The city's report calls for "no material impact" to the marine exclusion zones (MEZs). These are safety buffer areas that keep boaters away from the ends of the runways, their limits marked with buoys. It's not clear how a longer runway would affect the location of those exclusion zones.

Opponents of expansion say that extending the runway 400 metres would logically mean that the exclusion zones would have to be moved by that much as well. The TPA insists that the buoys won't have to be shifted further into the lake.

In an e-mail this week, a Transport Canada spokeswoman said it cannot "speculate" about "potential impacts" on the MEZs without having received more information from the TPA.

Another concern raised by opponents is that light towers may need to be installed in the lake, to the east and west from the MEZs. That's flat-out wrong, counters TPA executive vice-president Gene Cabral. He said that this so-called precision lighting will not be needed – the airport's current lighting "will not change in a CS100 scenario." Transport Canada declined to comment on this as well and the city says it is seeking more information.

Also yet to be determined is whether the airport would need barriers to contain the engine blast from the new aircraft.

Opponents raise the spectre of high walls enclosing the runway while the TPA acknowledges the possibility of walls at each end of it. "The CS100 may or may not have a jet blast that is of any effect or any consequence," said Geoff Wilson, CEO of the TPA. "It's part of the environmental assessment that we would do."

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Traffic problems

The proximity that is the island airport's main calling card is also one of its biggest liabilities.

Immediately to the north of it, across a narrow channel of water, is a bustling little neighbourhood complete with school, parks and residential buildings. And while it would be unfair to blame the airport for all the traffic problems in the area, opponents say that congestion needs to be addressed before expansion can be considered.

A city-commissioned report published last year gives an idea of the problem, with substantial rush hour delays at nearby intersections. While there are traffic signal adjustments that could improve the situation, the report says, adding jet-related traffic would largely wipe out those gains. On Eireann Quay itself – which leads to the airport ferry – traffic would go up 20 per cent if jets are allowed, unless people start switching from taxis to the shuttle.

Mr. Livey this week made clear the city's position that the TPA would be on the hook for between $15-million and $20-million worth of traffic improvements before jets could be approved. On this as well the TPA declined comment, but the city's position contradicts its earlier stance that it can ill afford to do more.

Mr. Wilson said last month that the port authority is doing what it can to reduce traffic on the mainland side, with a new staging area for taxis and a coming pedestrian tunnel that should reduce the bunching of passengers.

The TPA hopes as well that more shuttle buses will encourage an increase in the number of airport passengers using these vehicles. The shuttles now carry 25 per cent of passengers, a number that would need to rise to 35 per cent to blunt the impact of the greater passenger numbers, according to the city report.

But the bigger-picture solution is a multimillion-dollar plan to infill a bit of lake and create a new access route into the site. The TPA would like this to come from Ottawa but a formal application has not been made.

And Mr. Livey said the city's clear position is that this money cannot come from the Building Canada fund. "It will not be robbing Peter to pay Paul," he said. "It would have to be a self-sustaining, free-standing set of dollars for us to be able to make that work."