Don't know if it is 10 but in the last few years we have had almost every flight delayed or cancelled. We live in the IAD area and travel at least once a year or more iad/lhr and onward. Couple of years ago was one of the worst. We got stranded at lhr for 6 plus hours. In 2020 we had a flight scheduled vie/lhr/iad. The vie/lhr leg was canceled. The routing they offered were ridiculous. I ended up having to buy Austrian air vie/iad in bus. for $6000.00.