An account executive, just home from a first date, fell to her death in Midtown East early this morning, when the railing of her 17th floor balcony she was sitting on gave way, police sources said.

Jennifer Rosoff, 35, invited her date to her place and the two went on the balcony of the East 57th Street and First Avenue apartment for a smoke about 12:30 a.m., sources said.

The date told cops that he heard two sharp pops before the railing collapsed under Rosoff and sent her flying backward off the tiny balcony, sources said.

She landed atop construction scaffolding on the second floor, police said.

Rosoff, who worked as an account executive for the Flatiron-based web marketing firm TripleLift, died instantly, cops said.

A neighbor from the 14th floor heard the date’s screaming and came of his apartment to see what had happened.

“There was a man who was hysterical and crying by the elevators. He told me that he and Jennifer were on their first date,” the neighbor, who asked not to be named, told The Post.

“They had just gotten back and she was showing him her apartment. Then he said they stepped out onto the balcony and had a drink. She was leaning on the balcony, then the railing gave way and just snapped.”

Another neighbor said she heard the horrific sound of Rosoff’s body hitting the scaffolding.

“I heard the thud last night,” said neighbor Sara Shubert, who has lived at 400 E. 57 for eight years.

“I heard from my friend that she saw a man come out of the main lobby elevator frantic, and screaming, ‘My friend fell! She fell off the building’.”

A spokeswoman for Stonehenge Management, which has managed and owned the property for the past year, said in a written statement:

“This is a tragedy and our sincere condolences go out to the family and friends of Ms. Rosoff. I am trying to reach out to the family to express these sentiments personally. We are cooperating fully with the investigation into the cause of this terrible accident.”

Neighbors had no complaints about the management agency, and buildings officials had recorded no open violations.

“It really makes no sense that the railing would break because this building is just about perfect,” said resident Pearl Harrison, 86.

“No one in this building has issues with the management. This seems like a freak accident.”

Additional reporting by Jeane MacIntosh, Antonio Antenucci, Dan Prendergast and Yoav Gonen.