WASHINGTON : The US National Transportation Safety Board recommended Tuesday that the Boeing Co. 737 NG be redesigned to prevent a repeat of an incident last year in which the structure in front of the engine came apart in flight, killing a passenger.

More than 7,000 planes could be affected by the recommendation that the inlet to the engines be redesigned to contain parts that come loose in a failure.

The NTSB called on the Federal Aviation Administration to require the repair be installed on new 737 NG aircraft and that it be retrofitted onto the thousands of planes in service.

The safety board issued the recommendation after a hearing Tuesday on the April 17, 2018, incident in which a woman was partially sucked out from the Southwest jet and had to be pulled back into the plane by fellow passengers.

A fan blade on an engine made by CFM International Inc. broke off, triggering the damage, the NTSB concluded.

Boeing slid as much as 2.1% after the NTSB’s comments, reversing gains from earlier in the session. The shares were little changed at $369.74 at 12:38 p.m. in New York.

A Boeing representative did not immediately have a comment.

The NTSB stopped short of asking for changes on other aircraft and engine combinations, but asked the FAA to improve how the structure at the front of the engine -- a curved surface that provides a smooth flow of air into the power plants -- is designed in the future.

The NG model is a predecessor to Boeing’s 737 Max that has been grounded since the second of two deadly crashes in March.