More than half of all flights in and out of some of Canada's major airports are being cancelled or delayed, recent data has shown.

DataWazo, a data strategy agency based in Fredericton, N.B., has been tracking the data as frustrations mount in Canada over lengthy airport delays, due in part to increased summer travel and not enough airport staff.

Between June 22 and 27, 51 per cent of domestic and international flights at some of Canada's biggest airports, including Toronto Pearson, Montreal Trudeau International, the Ottawa international Airport, Calgary International Airport and Vancouver International Airport, were either delayed or cancelled. The worst was Toronto Pearson where 11 per cent of flights during that same time period were cancelled and 52 per cent of flights were delayed.

"There was some kind of hope for a reprise when the mandates were lifted on the 20th. That hasn't been seen in much capacity yet," DataWazo owner Ray Harris told CTV National News.

"The numbers are about the same pre-20th and post-20th. It just doesn't seem to be getting better."

The federal government removed a requirement on June 20 for domestic and international outbound travellers to provide their proof of vaccination when travelling by plane or train.

Pushed by the tourism and airline sectors, they believed the move would help increase staffing levels.

However, documents presented to Parliament and reviewed by CTV National News show the Canada Border Services Agency (CBSA) had 1,904 officers working at airports in Canada as of May 1, 2022, below 2,033 on Jan. 1, 2020 and 1,981 on Jan. 1, 2016.

As of May 4, 2022, 103 CBSA employees were on unpaid leave due to their vaccination status. CBSA officers facilitate the flow of incoming international travellers, and are responsible for checking documentation from passports to proof of vaccination.

Meanwhile, the documents show there were 6,867 people employed by the Canadian Air Transport Security Authority's (CATSA) third-party contractors to do airport security screenings as of May 16, 2022.

This is compared to 7,420 active screening officers on Jan. 1, 2020, and 5,509 on Jan. 1, 2016.

Six CATSA employees were on unpaid leave due to their vaccination status as of June 14. CATSA is responsible for passenger and baggage screening at Canadian airports.

Transport Minister Omar Alghabra says while the federal government anticipated a return to travel, few predicted the surge happening now.

But he says 91 per cent of passengers currently waiting in CATSA lines are being processed within 15 minutes or less, which he called a significant improvement from three or four weeks ago.

"On our end, we have done everything we can that is within the control of the federal government," he said. "Now, we need to work with airlines and airports at dealing with the flight delays and luggage handling issues because we need the cooperation of airlines and airports to address these issues."

Mark Weber, national president of the Customs and Immigration Union, says the number of front-line workers has experienced a "slow erosion" for some time.

"So right now, we are hiring the same amount as we hired last year and the year before. The numbers that were hiring are just basically covering attrition," he said.

Meanwhile, the CBSA is imposing mandatory overtime and suspending non-essential training under its "summer action plan."

Even if more people were hired this year, Weber says under the current system an individual must go through 18 weeks of training and one year of apprenticeship before becoming a full officer.

"So to address things for this summer, that ship has kind of sailed."

With files from CTV News and The Canadian Press