Public hearings begin this morning into an incident at the Ottawa International Airport last month that left passengers aboard two redirected airliners stranded on the tarmac so long that some of them called 911 for help.

Maryanne Zehil was a passenger on the Air Transat flight, and will take part in the Canadian Transportation Agency inquiry that starts Wednesday. Air Transat Flight 157 from Brussels was originally scheduled to arrive in Montreal on the afternoon of July 31, but was diverted to Ottawa due to thunderstorms. The flight landed at the Ottawa airport just after 5 p.m. ET after more than eight hours aloft.

It sat on the tarmac for another six hours, and passengers weren't allowed to deplane.

Passengers complained the air conditioning in the cabin wasn't working despite an outside temperature of 28 C, and said they weren't offered sufficient food or water. Several passengers resorted to calling 911 to report an emergency.

Paramedics arrived, the plane doors were opened and passengers were eventually given water.

The Canadian Transportation Agency (CTA) launched an inquiry into the incident, as well as Air Transat Flight 507 from Rome, which sat on the tarmac in Ottawa for almost five hours. The CTA has set aside two days for public hearings at its Elgin Street office in Ottawa.

The agency called on passengers and organizations involved in the incident to testify at the hearings, which will be broadcast live online.

'A horrendous experience'

Maryanne Zehil was on the plane from Brussels and plans to take part in the hearings.

"It was really a horrendous experience," said Zehil, who has kept in touch with other passengers who were also on the flight. "We're doing all this so something can change. We think it's unacceptable."

Laura Mah and her husband Chris Mah snapped this selfie when the plane first landed in Ottawa. (Submitted)

The inquiry will look into whether Air Transat followed its tariff — a contract between an airline and its passengers — and whether that tariff is reasonable, according to the CTA's website.

According to Air Transat's tariff, it must offer passengers the option of getting off a grounded plane after 90 minutes.

The CTA has the power to order the airline to compensate passengers for out-of-pocket expenses, as well as other corrective measures.

Air Transat has already offered to pay each passenger $400 on the flight from Brussels in what the airline called "a gesture of good faith" because the air conditioning wasn't working. Passengers on the other flight say they haven't been offered any compensation for their troubles.

Parents struggled to keep kids cool

Laura Mah, another passenger on the Brussels flight, said she has yet to see that money. She said she witnessed parents desperately trying to keep their children cool and hydrated, and pleading with flight attendants to open the doors.

"That's horrifying," said Mah. "Nowhere else would that ever be allowed."

Zehil, who said she witnessed another passenger suffer a panic attack, and whose dog was below in the cargo hold without water for 16 hours, has submitted her testimony to the inquiry and will answer any questions via Skype from Montreal.

"We think there should be a law that obliges them to get us off the plane after a while," said Zehil.

Air Transat has blamed "a confluence of factors beyond [its] control" for the delay. The airline said a request to refuel in Ottawa was turned down, and neither portable stairs nor power units were made available while the plane was on the tarmac.

The Ottawa International Airport Authority disputes that account.

Public hearings rare

It's relatively rare for the CTA to hold public hearings into such incidents. This inquiry is only looking into the July 31 incident, and won't delve into industry-wide standards when it comes to tarmac delays.

In addition to passengers, the list of witnesses expected to testify at the hearings include the CEO of the Ottawa International Airport Authority, the president of Air Transat, the director of ground services with First Air Operations and an airport official in charge of refuelling planes.

Public consultations on the broader question of air passengers' rights are expected once Bill C-49, known as the Transportation Modernization Act, is passed.