NO AMOUNT of statistical evidence on the relative safety of flying as a mode of transportation can erase the horror of last Sunday's crash in Detroit or abate significantly the public uneasiness that follows any such air tragedy. Even though a million passengers may be in the skies every day -- and even though in 1986 they traveled some 300-plus billion miles without a single fatality -- the fate of Northwest Flight 255 on that one terrible evening continues to fascinate people from coast to coast. What went wrong?

The answer will take time and the considerable expertise of federal investigators, whose preliminary findings have come to focus on the position of the plane's flaps and the apparent silence of the computerized voice that is supposed to warn the pilot and copilot that vital flight controls were not set upon takeoff. As staff writer Douglas B. Feaver has reported, preliminary findings in this investigation raise some sensitive questions that have come up in connection with other air catastrophes over the years. Was there a failure on the part of the pilot and copilot to carry out some routine procedure? Or was there an equipment failure that might also be attributable to a human error?

According to specialists, the accident may have happened because of the convergence of two improbable events: the failure of the pilot and copilot to set the flaps and the failure of warning systems to tell them of their omission, perhaps because a circuit breaker for this warning system was not set or had been damaged somehow.

In the absence of more detailed findings, assumptions about human error or insufficient training or poor safety inspections should be resisted. This is precisely why investigators may take nine months to a year before issuing a final report. Similarly, there are no apparent grounds for linking the disaster in Detroit to heavy traffic in the skies, to any failures of the air traffic control system or to that catchall broadside of some air travel critics: deregulation. There is much more to be learned.