Lawyers representing victims of the Amsterdam air crash in February this year are starting legal action against aerospace company Boeing in the United States this week.

When the Turkish Airlines Boeing 737 crashed in a field close to Amsterdam’s Schiphol Airport, nine of the 134 passengers were killed and 80 were injured. The investigation concluded that the most likely cause of the crash was a faulty altimeter compounded by pilot error.

The lawyers representing the victims say Boeing was aware there was a problem with the radio altimeter in its 737 aircraft prior to the crash, newspaper Trouw reports. Shortly after the disaster, a Boeing internal memo dating from before the crash was leaked. It indicated that that the plane’s left altimeter had given faulty readings on other flights in recent years. In the case of the Turkish Airlines crash, the altimeter gave a negative reading, prompting the autopilot to start a landing. The pilots intervened too late.

One of the lawyers representing the crash victims in the Chicago court case, Frans Vreede, says pilots and aviation experts put the problem down to a design fault. Although 737s have two altimeters, only the left one communicates with the automatic throttle. He claims Boeing failed to fit the aircraft with a back-up “competitor” altimeter simply to cut costs.