When they boarded a small plane bound for upstate New York this past weekend, the six passengers — a pair of close-knit siblings, their parents and partners — were on the cusp of a new chapter in a family life already replete with personal and professional accomplishment.

A private plane that crashed in upstate New York over the weekend was carrying a close-knit family of physicians and distinguished recent student-athletes, bound for a trip to the Catskills for a birthday celebration and the Passover holiday.

It was unclear as of Saturday what had caused the plane that was carrying six people to crash near Copake, N.Y.