From www.planepull.com:

Plane Pull Canceled Due to Severe Weather Predictions
 
The Dulles Day Family Festival, featuring the 16th annual Plane Pull, was scheduled to take place tomorrow, Saturday, Sept. 6, at Washington Dulles International Airport.
 
Due to severe weather predictions from the approaching Tropical Storm Hanna, this event has been canceled. There is no rain date.
 
The Metropolitan Washington Airports Authority and Special Olympics Virginia would like to thank all of the Plane Pull teams, sponsors and volunteers for their support of Special Olympics Virginia. We are looking forward to sunny weather at next year’s event.

Thanks Audrey for the heads up!!!