DETROIT -- Federal investigators made public new information yesterday suggesting that visibility at Detroit Metropolitan Airport might have been below the legal minimum on Dec. 3, when a Northwest Airlines DC-9 jetliner got lost in the fog, wandered onto the wrong runway and was struck by another jet.
The pilots of both planes said moments before the accident, which killed eight people on the DC-9, that visibility might be too poor to fly. A controller in the tower told investigators of the National Transportation Safety Board that she thought so, too, the investigators said.
The controller who decided that visibility was good enough to permit flights to take off has told investigators that he made this judgment without referring to a chart that is supposed to be used for such decisions, according to documents made public yesterday.
The chart lists landmarks and distances at the airport.
The controller, Armando M. Gonzalez, simply looked out the tower's window and made an estimate of visibility.
Opening a week of hearings into the accident, the safety board made public some reports and exhibits showing that many pilots thought visibility was below the minimum of a quarter-mile, or 1,320 feet, and that one controller estimated that it was only one-eighth mile.
Several times in the 10 minutes they spent trying to find their way while taxiing across the airport, the DC-9 pilot, William V. Lovelace, and his co-pilot, James Schifferns, complained about the poor visibility.
"It looks like it's going zero-zero out there," Mr. Schifferns said, using aviation jargon for when nothing is visible. Later, Mr. Lovelace said, "We've got to be below minimums."
In the tower, too, there was uncertainty over visibility.
One controller, Marianne Frances Becker, told investigators that she used the chart of landmarks to estimate visibility at one-eighth mile, below federal limits. Ms. Becker said she asked the controller in charge of making the official estimate of a quarter-mile whether he wanted to change it.
He told her he did not, she said.