US flight delay stats don't tell full story

[WASHINGTON] Flight delays are significantly undercounted at some of the biggest US hub airports, skewing airlines' on-time performance statistics disclosed to travellers, according to an inspector general's report.

Statistics for carriers such as American Airlines Group, Delta Air Lines and United Continental Holdings don't include late arrivals by regional partners that account for almost one-fourth of US flights and are exempt from reporting delays, the Transportation Department report said.

Philadelphia International Airport, for example, had 38,000 tardy flights in 2012, more than twice the official count of 13,800 published by the Department of Transportation's Bureau of Transportation Statistics, the study found.