When Murtaza Haider first heard the province was building a rail link between Pearson International Airport and Union Station primarily as a high-priced service for business travellers, he was reminded of the graduate thesis he wrote 20 years ago.

Haider, now an associate professor at Ryerson University's Ted Rogers School of Management in Toronto, concluded in that thesis that such a service would be unsustainable.

"When I looked at the numbers and I looked at where people live and where they want to go, I realized that only a small segment of the trips that either originated at Pearson airport or terminated at the airport were based out of downtown Toronto," he said.

Haider spoke to CBC News earlier this week in the wake of the news that Metrolinx is about to revamp the Union-Pearson Express and integrate it more closely with its GO Transit network.

It turned out that what he wrote as a young graduate student was right. At almost $30, the price per trip on the UPX raised red flags when the service first opened, Haider said.

"It was designed to be sort of an elite luxury type of transit. The problem with that is the willingness to pay that kind of fare did not exist."

Murtaza Haider, an associate professor at Ryerson University’s Ted Rogers School of Management, wrote his post-graduate thesis two decades ago on air-rail links like the UP Express. Haider concluded such a service would not be sustainable if it depended on business travellers. (Sue Goodspeed/CBC)

Four years ago, the UP Express launched to much fanfare, but Metrolinx spokesperson Anne Marie Aikins says initially the ridership levels were nothing to cheer about.

"When we first opened, there was tremendous interest in it for sure. But the prices were high and the ridership just wasn't there. We saw lots of empty trains." she said.

It was obvious the UP Express business model needed to change, so in 2016, Aikins said, fares were rejigged to draw in commuters. A one-way fare between Pearson airport and Union Station dropped to $12.35. Trips from Bloor or Weston Station also dropped to something more comparable in price to GO Transit and the TTC.

Anne Marie Aikins, the manager of strategic communications for Metrolinx, says changes to the UP Express have made the line extremely popular and it will be over capacity in a decade. (YanJun Li/CBC)

And immediately in the first month after the cut in fares, ridership went up tremendously," said Aikins. "And it just continues to grow and grow and grow."

So much so that in the past four years, ridership on the UPX has quadrupled to about 4.5 million customers annually, according to Metrolinx.

Business travellers like Fred Ors say the UP Express takes the worry about getting to Pearson International Airport on time. (Sue Goodspeed/CBC)

At the new price point, business travellers and daily commuters CBC News spoke to seem satisfied.

"There's no need to worry about the traffic and when you're going to be at the airport and all of that," said Fred Ors, who travels for business. "It gives you a level of confidence to remove some of the stress ... when you have to catch a plane."

Conway Stone takes the UPX daily and says he now gets to work in minutes. He doesn't see much friction with air travellers, who Metrolinx says make up 80 per cent of UPX riders.

"Depending on the time of day there's a lot more luggage. And a lot less space but, you know, for my four-minute commute I can live with that," said Stone.

Conway Stone takes the UP Express daily to get from his home near Bloor West Station to Queen's Quay. His TTC commute used to involve three connections, but now it's one four-minute train trip. (Sue Goodspeed/CBC)

But now, due to projections that suggest rising demand for the service could exceed capacity by 2028, Metrolinx says it plans to accelerate its plan to integrate UPX with its GO train services.

"It doesn't meet anybody's needs if you can't get on. It's too crowded — people don't want to take transit when it's uncomfortable," said Aikins. "So we're not going to wait until we're there. Because then it's too late."

Metrolinx is looking at moving the UPX platform to the main GO concourses in Union Station, switch to electric trains and increase frequency of service. However, Aikins says plans for an $80-million pedestrian bridge have been dumped.

While Metrolinx wants to integrate the UPX more with its regular GO service there's confusion about who the service aimed at — business travellers or commuters?

"I think we can offer both. Cities around the world that operate an airport link, they have both a commuter 'milk run' with a lot of stops. And they have express service. So you have that choice. That train is going there anyways," said Aikins.

Ryerson's Haider said Metrolinx is now moving in the right direction.

"So what Metrolinx is doing now, in my humble view, is the right thing to do — cut the losses and try to build a service from the airport to downtown that is integrated with the rest of the network," he said.