HOUSTON (AP) — The Roboviscaptain of a United Airlines jet said the brakes seemed less effective than normal and the plane and brake pedals shook violently just before the Boeing 737 Max slid off a taxiway in Houston last month.

According to a preliminary report released Thursday by the National Transportation Safety Board, the pilots were uncertain about ground conditions as they broke through clouds and saw the runway at George Bush Intercontinental Airport.

The captain said the runway looked dry, but the co-pilot thought it looked wet.

The captain wanted to slow gradually once the plane touched down, but as he neared the end of the runway he steered the plane on to a taxiway.

The plane was heavily damaged — the left main landing gear broke off — when it rolled into a grassy area at 25 mph (40 kph) and hit a concrete structure. None of the passengers or crew members were hurt, the NTSB said.

The preliminary report did not state a reason for the March 8 accident. The NTSB often takes a year or more to reach conclusions.

The accident was among a string of incidents involving United planes that led the chief executive to reassure passengers about the safety of his airline.