Elizabeth Williamson reports on the White House.

The mystery begins in a Pittsburgh bar where several high-flying airline types met last month.

The group swapped stories over drinks when three people present let loose with a good tale. Bo, the presidential puppy, recently left a present on the presidential jet, they said, and a flight attendant had nearly stepped in it.

Associated Press Bo, the Obama family dog, walks away from Air Force One Aug. 30, 2009, at Andrews Air Force Base, Md., upon the Obamas’ arrival from a vacation in Martha’s Vineyard. (AP Photo/ Alex Brandon)

“You can imagine the horror on board when they discovered what it had done,” a participant in the conversation said, referring to Bo.

Reports of other puppy-like behavior support the story. At least two reporters spotted Bo running loose aboard Air Force One this summer. News stories say he chews socks, magazines and the presidential sneakers. In an NBC television interview around the time of the alleged accident, President Barack Obama said Bo has chosen notable venues in the past…