31.   But it was not in place because the FAA had not clearly determined who was to draw up the requirements for the system, the safety board said.

32.   But officials of the unions and the safety board say the sensors need not go on every bridge.

33.   But the airline re-checked five times and found that the play was well within tolerances, the safety board said.

34.   But the motorman told investigators from the safety board that it was green.

35.   But several senior criminal investigators said they were surprised that the safety board had not been more involved in the interviews from the start.

36.   But the safety board has its own macho culture, a combination of the calm fearlessness of pilots and the analytical confidence of engineers.

37.   But the safety board steered clear of placing prohibitions on young trainees.

38.   But the safety board says the cameras could provide valuable details on the cause of many crashes.

39.   But the safety board issues only recommendations, not rules.

40.   But the safety board said that this belief was obsolete, because such an effect is not possible on modern aircraft.