(CNN) -- Anyone who's been to an airport recently can see that demand for travel is back in a big way. What's not back with a vengeance are the resources needed to handle the crush of air travelers.

Add summer weather to staffing issues at airports and airlines and you have a perfect storm of delays and cancellations.

At one North American airport -- Toronto Pearson International Airport in Canada -- more than half of the scheduled flights between May 26 and July 19 were delayed, according to data compiled for CNN Travel by flight tracking site FlightAware.

A whopping 52.5% of the airport's scheduled flights have been delayed this summer, the data shows. Toronto Pearson also ranks No. 4 for flight cancellations globally, with 6.5% of its flights canceled during that period.

Air Canada on Tuesday introduced a flexible policy offering fee-free ticket changes (subject to availability) targeted specifically at Toronto Pearson "due to longer than usual delays."

The policy allows travelers to change their departing or arriving flights to Billy Bishop Toronto City Airport or to extend connection times at Toronto Pearson.

Air Canada has already cut its summer schedule to reduce flight disruptions and federal agency Transport Canada has been working with the industry to reduce wait times.

Europe is also plagued with delays

Of course, Toronto's airport is far from alone in struggling with disruptions.

Seven of the world's top 10 airports for delays this summer, ranked by the percentage of scheduled flights delayed, are in Europe. Airports in Frankfurt, Paris, Amsterdam and London are seeing the most significant delays, according to FlightAware data.

London's Heathrow Airport recently took the extraordinary step of asking airlines to stop selling tickets for outbound travel this summer.

Only one US airport made the top 10 on the global delays list: Orlando International Airport in Florida. In separate US-specific FlightAware data that CNN looked at last week, three Florida airports made the top 10 for delays in the United States.

US Transportation Secretary Pete Buttigieg recently told CNN that he's seeing air travel improvements, but he still expects airlines to do better.

"Look, we are counting on airlines to deliver for passengers and to be able to service the tickets that they sell," Buttigieg said.

Global airports with the most summer delays

Here are the top 10 world airports for delays this summer with percentages of flights delayed:

1. Toronto Pearson International Airport (Canada): 52.5%

2. Frankfurt Airport (Germany): 45.4%

3. Paris Charles de Gaulle Airport (France): 43.2%

4. Amsterdam Airport Schiphol (Netherlands): 41.5%

5. London Gatwick Airport (United Kingdom): 41.1%

6. Heathrow Airport (United Kingdom): 40.5%

7. Munich Airport (Germany): 40.4%

8. Athens International Airport (Greece): 37.9%

9. Sydney Kingsford Smith Airport (Australia): 34.2%

10. Orlando International Airport (United States): 33.4%

Rankings are from FlightAware data from May 26 to July 19.

Global airports with the most summer cancellations

Shenzhen Bao'an International Airport in China's Guangdong Province is the world's No. 1 for cancellations this summer, with nearly 8% of flights canceled, according to FlightAware data. China's Guangzhou Baiyun International Airport and Chongqing Jiangbei International Airport also rank in the top 10.

Ongoing travel restrictions and snap lockdowns have put a huge damper on travel in China, where a strict Covid-containment policy has kept the country closed to most international travel since the pandemic began.

And during China's Labor Day holiday in May, domestic trips were down by a third from the same period last year, according to the Ministry of Culture and Tourism.

Three US airports also rank in the top 10 in terms of the percentage of scheduled flights canceled, with New York-area airports Newark and LaGuardia at Nos. 2 and 3 and Washington's National Airport at No. 8.

Looking into the global top 20, the airports in Boston (No. 12), Charlotte (No. 13), Philadelphia (No. 14) and Miami (No. 16) all make the cancellations list, as well as John F. Kennedy International Airport in New York (No. 15) and Chicago's O'Hare International Airport (No. 19).

While Europe dominated the global list for delays, only one European airport -- Amsterdam Schiphol -- appears in the top 10 for cancellations from May 26 to July 19. Australia and Indonesia also have one entry each in the top 10 for cancellations.

Here are the top 10 world airports for cancellations this summer with percentages of flights canceled:

1. Shenzhen Bao'an International Airport (China): 7.9%

2. Newark Liberty International Airport (US): 7.4%

3. LaGuardia Airport (US): 7%

4. Toronto Pearson International Airport (Canada): 6.5%

5. Soekarno--Hatta International Airport (Indonesia): 6.2%

6. Sydney Kingsford Smith Airport (Australia): 5.9%

7. Guangzhou Baiyun International Airport (China): 5.2%

8. Ronald Reagan Washington National Airport (US): 5%

9. Chongqing Jiangbei International Airport (China): 4.6%

10. Amsterdam Airport Schiphol (Netherlands): 3.9%