The federal government’s transportation agency has launched an inquiry after two Air Transat flights were diverted from Montreal to Ottawa on Monday and sat on a tarmac for several hours.

The Canadian Transportation Agency says it has ordered the airline “to explain the circumstances surrounding a delay of two of the airline's flights."

The CTA says it’s looking into whether the airline “respected its terms and conditions of carriage for international flights (tariff) with respect to the treatment of passengers on the aircraft.”

Scott Streiner, chair and CEO of the CTA, said in a written statement that the agency is committed to ensuring passenger rights are respected.

“This inquiry will determine, based on the evidence and the law, whether the treatment of passengers on the two flights was in line with the airline's obligations -- and if not, what corrective measures should be ordered,” Streiner said.

“We'll get it done as quickly as possible, but we'll take the time required to gather all the facts,” Streiner added.

Dozens of Air Transat flights were diverted from Montreal to Ottawa on Monday, due to bad weather in Montreal.

An Air Transat flight from Brussels sat on the tarmac for about six hours. Passengers told CTV News that the air conditioning was not working properly and cut out completely at one point. At least one person called 911.

Air Transat issued a statement Tuesday afternoon apologizing for “inconveniences” that it said were “caused by a situation that was beyond our control.”

“Ottawa airport staff were unable to provide with loading bridges or stairs that would have enabled the passengers on the Brussels flight to disembark or our ground crews to replenish the aircraft’s empty drinking water reservoir,” the airline said.

The airline added that a “fuel shortage” resulted in the lack of air conditioning.

Ottawa Airport spokesperson Krista Kealy told CTV News on Tuesday that it is “up to the airline” to decide whether the passengers get off a plane and she questioned Air Transat’s assertion that there were no air stairs available.

“We’re very disappointed that [Air Transat] chose to say that some of the resources were not available to them,” she said. “There were air stairs available in the event that they did want to offload the aircraft.”

Air Transat posted a statement on its Twitter account around 7 p.m. Tuesday that said “Ottawa Airport’s version of events is not consistent with ours.”

“We will continue our investigation and come back with the facts as soon as possible,” the statement went on. “In any case, our passengers experienced genuine discomfort for which we are sincerely sorry.”