A fault in software used by most US airlines caused a wave of flight delays this morning across the US, affecting hundreds of flights. "Several airlines are experiencing issues with a non-FAA flight planning weight and balance program called AeroData," a Federal Aviation Administration spokesperson said in an e-mailed statement. "Mainline operations and regional operations are affected to varying degrees."

That software, provided as a service by AeroData Inc., is used to perform weight and balance calculations needed for flight planning—which is particularly important for airlines operating regional and commuter flights. Today's software outage only lasted for about 40 minutes, but it had a rippling effect across the US.

Southwest Airlines was the most heavily affected by the outage as the airline had to delay 620 early flights. SkyWest, a commuter airline affiliated with United and Delta Airlines, had over 200 flights delayed. United Continental had about 150 regional flights delayed.

AeroData, based in Scottsdale Arizona, is a family-owned corporation with a very low profile on the Internet. According to the company's public website (which hasn't been updated since the company moved from Colorado to Arizona in 2008), AeroData won a 1990 contract with the FAA to "distribute its public domain data." In addition to the weight and balance system, the company also provides airlines with aircraft performance data, other aircraft management applications, and a "compute server system" to host these services.

A Web portal to access the company's software (based on Flash and Microsoft Studio 7.0) was last updated in 2009. The portal advises visitors, "We will be enhancing our Web site in the coming months using Microsoft Silverlight technology." Access to the portal is controlled by customer credentials and IP address.

Ars attempted to reach AeroData for comment, but we received no response. We will update this story if more information becomes available.