“It is 'normal' to expect around 1 to 2 percent of flights to be canceled,” said Gary Leff, author of ViewFromTheWing.com. He added that around 20 to 25 percent of flights are late by at least 15 minutes, though it's harder to track the range of how delayed flights are.
How late does a flight have to be to be considered delayed?
A flight delay occurs when an airline flight takes off and/or lands later than its scheduled time. The United States Federal Aviation Administration (FAA) considers a flight to be delayed when it is 15 minutes later than its scheduled time.