Corrosion was found in six Aloha Airlines jetliners, including a Boeing 737 whose top came off over Hawaii, witnesses testified at a federal hearing on the fatal April 28 accident.

The testimony came Tuesday on the first day of the National Transportation Safety Board hearing on the accident, in which a flight attendant on the 19-year-old aircraft fell to her death and 61 of the 94 people aboard were injured.In addition to the 737, corrosion was found this spring on three Aloha planes and on two of the airline's other 737s, one of which had a 71/2-inch crack, the five-member panel was told.

The hearing, which was to resume Wednesday and end Friday, is aimed at trying to determine the accident's cause and what lessons can be learned on the safety and maintenance of older aircraft.

Panel Chairman John K. Lauber asked Thomas Derieg, Aloha vice president of operations, whether photos showing heavy corrosion on the skin of two of the airline's 737s in early May reflected an adequate corrosion prevention program.

"If you find the corrosion and correct it, it's working," Derieg said. "I don't like to see pictures like this, and if I see it in the future I will certainly challenge what's going on and how we're doing business."

One of the two planes was completely rebuilt and repaired, while the other was removed from the fleet, as well as the accident aircraft and two other heavily used airplanes, Aloha spokesman Milton Goto said later.

John Mapel, a Federal Aviation Administration aviation inspector, said he found corrosion on an Aloha jet April 14, the same day Boeing Co. officials say they met with airline officials to express concern over maintenance of Aloha's aging aircraft.

Aloha immediately grounded the plane for repairs, Mapel said.

Mapel said neither Boeing nor Aloha told him about reports of corrosion before this spring. "I think both of them should have told me," he said.

Mapel said Robert L. Oldani, manager of Boeing maintenance and operation systems, barred him from the April 14 meeting.

A Boeing official refused to comment on Mapel's testimony.