Fifty years ago tomorrow tragedy struck.

On December 16, 960, 134 people lost their lives when United Airlines Flight 826 and TWA Flight 266 collided over the skies of Staten Island. The United aircraft crashed down at the intersection of Sterling Place and Seventh Avenue.

Destruction rained down on the streets of Park Slope on a cold wintry day just like today.

An 11-year-old boy survived for 26 hours after the crash. He died at Methodist Hospital, where there is a plaque. People on the ground died, too, including a Xmas tree salesman, a church caretaker, a doctor walking his dog. Many buildings were destroyed.

On Thursday, Dec. 16, 2010, at 9:45 a.m. — 50 years to the day of the tragic crash — Green-Wood Cemetery will be honoring those who perished, both in the sky and on the ground, by unveiling a new eight-foot memorial. The granite monument will stand sentinel near the gravesite where the unidentified remains of victims have rested for half a century.

This special unveiling ceremony and memorial service, sponsored by Green-Wood Cemetery, is free to the public. Participants should gather at the cemetery’s main entrance at 25th Street and Fifth Avenue at 9:45 a.m. The service will begin promptly at 10 a.m. (RSVP with Isabella Vlacci at 718-210-3024).