WASHINGTON, April 25 The National Transportation Safety Board recommended Tuesday that the Federal Aviation Administration change how it approves new airplane designs, saying that problems with the process contributed to four crashes from 1994 to 2001 that killed more than 700 people.

The safety board, an advisory body, emphasized that airline flying was extremely safe over all, but that the four accidents had killed 60 percent of those who died in jet crashes over the period.

Past shortcomings in design review are important because a new generation of jets is being tested or designed, and includes new challenges. The newest planes require software that must be analyzed and maintained. They also have composite materials developed relatively recently. In addition, the design of computerized cockpits must be studied.

The report that the safety board issued Tuesday did not provide new details about the four crashes but did link them as part of a trend.

The board said an Alaska Airlines plane crashed off California in January 2000, killing 88 people, because of a failure of a part that controlled the horizontal tail. The problem was traced to the airline's change in the maintenance procedure for the part, whose design was approved by the F.A.A. in 1965.

The change was made without sufficient analysis of the design, and the F.A.A. did not preserve enough details about the assumptions behind its 1965 decision, board staff members said.

In the case of Trans World Airlines Flight 800, a Boeing 747 that exploded off Long Island in 1996, killing 230 people, the design problem involved the fuel tank.

In the case of USAir Flight 427, a Boeing 737 that crashed near Pittsburgh in September 1994, killing 132 people, the board pointed to assumptions about a backup system for a valve that controlled the rudder.

American Airlines Flight 587, an Airbus A300 that had just left Kennedy Airport in New York, crashed in November 2001 in part because the pedals used to control the rudder of the plane were difficult to use properly at the speed the plane was flying. That crash killed 265.

The board sent three recommendations to the F.A.A. One was to list systems on each plane that are critical to safety, and preserve the "rationale, analysis methods, failure scenarios, supporting evidence and associated issue papers." Another was to include "human/airplane system interaction failures," in which the set-up of the controls can encourage error. The third was to use experience gained in the decades that a typical model is in use to check whether the assumptions underlying certification were correct.

John Hickey, the head of the Aircraft Certification Service at the F.A.A., agreed with some of the safety board's findings. The agency gathers extensive data on the performance of planes and components but does not now use it to see if the initial approval, or certification, was correct, he said.

The safety board chairman, Mark V. Rosenker, said, "every time we sit down to do an analysis, every time we study an accident, we come up with something we didn't know that we didn't know." For example, he said, before the Trans World Airlines Flight 800 crash, the F.A.A. did not know, or simply did not believe, that a spark could find its way into the fuel tank.