Terrain awareness technology that the National Transportation Safety Board (NTSB) has been pushing for since 2006 may have helped prevent the helicopter crash that killed nine people on Sunday – including NBA legend Kobe Bryant – but the FAA refused to make it mandatory.

The other crash victims were Bryant’s 13-year-old daughter Gianna; the pilot, 49-year-old Ara Zobayan, Christina Mauser, 38; John Altobelli, 56; his wife, Keri Altobelli, 46; their daughter Alyssa Altobelli, 13; Payton Chester, 13; and her mother, Sarah Chester, 45. All were involved with youth sports.

The NTSB recommended fourteen years ago that terrain awareness and warning systems (TAWS) be required on all U.S.-registered turbine-powered helicopters certified to carry at least six people.

The NTSB’s Jennifer Homendy said Tuesday that the Sikorsky S-76B helicopter that crashed Sunday in Calabasas, California was not equipped with a TAWS, which warns pilots when aircraft get too close to terrain.

The NTSB’s recommendation resulted from its investigation into a 2004 crash of a helicopter similar to the one in Sunday’s incident. That one, which occurred in the Gulf of Mexico, killed all ten people aboard.

The FAA did move to require TAWS on air ambulances, but not for all large capacity helicopters. In September 2014, after years of pressure, the NTSB closed the recommendation with an “unacceptable action” classification.

Homendy said Sunday’s crash was “high impact,” with the helicopter diving at a rate of 2,000+ a minute. Weather conditions at the time included thick fog that had grounded Los Angeles police helicopters.

The NTSB is expected to release a preliminary report on the crash within ten days.