Report: 'Blame the airlines for flight delays, not the weather'

“Blame the airlines for flight delays, not the weather.”

At least that’s the take from Bloomberg News, which crunched federal data and came to the conclusion that “airline miscues” such as mechanical issues and crew scheduling are now the leading cause of U.S. flight delays.

The Bloomberg report also comes on the heels of two high-profile systems glitches -- one experienced by Delta this month and another by Southwest in July -- put the subject of flight cancellations and delays back into the news.

Historically, weather and the USA’s heavily-used air traffic system have been chief causes of delayed flights. But that wasn’t the case for 2015, Bloomberg said after looking at flight-delay data from the federal Bureau of Transportation Statistics (BTS).

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Bloomberg writes “the swelling share of airline-caused flight delays marks a sea change from the days starting in 2003 when passenger outrage prompted regulators to require carriers to report the reasons flights were delayed. For much of the 2000s, late flights attributed to the aviation system far exceeded those by the airlines. That trend has gradually reversed itself, according to the U.S. data.”

Factoring into the shift are gradual air-traffic technology improvements and improved responses to adverse weather, developments that have reduced the number of delays attributed to the broad category dubbed “National Aviation System.” Also helping: Many of the nation’s biggest airlines have thinned their schedules following a wave of mega-mergers during the past decade, reducing over-scheduling at the nation's busiest airports.

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Airlines for America (A4A), the trade group that represents big U.S. airlines other than Delta, pushed back. For starters, a large percentage of flights were delayed “for undetermined reasons because the previous flight arrived late, something that reverberates through the system, according to the data,” Bloomberg writes.

“I do think that is a major part of the context that we need to be talking more about,” Sharon Pinkerton, A4A’s vice president for legislative and regulatory policy, says to Bloomberg.

Additionally, U.S. airlines have padded flight times on routes to congested airports in anticipation of system delays. That, Pinkerton argues, also helps obscure conclusions about delay trends.

For now, at least, passengers can take heart that delays have dropped to historically low levels in recent months. But it still can't hurt to hope for calm weather on the day of your next flight.

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IN PICTURES: 30 cool aviation photos

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