The National Transportation Safety Board held a two-day hearing on the January "door plug" blowout aboard a Boeing 737 Max 9 plane flown by Alaska Airlines.
Authorities received emergency calls at the same time about a structure fire and an aircraft that went off radar three miles from a Florida airport. It is still unknown how many fatalities there were.
The latest safety lapse at Boeing renews concerns about the company's influence in Washington and whether federal regulators have delegated too much of their oversight authority to its employees.
Regulators say they're increasing control of Boeing production after a panel blew off a 737 Max 9 jet, and will re-examine whether the company can be trusted to assess the safety of its own planes.
About 170 planes were grounded after the "door plug" on a Boeing 737 Max 9 blew out on an Alaska Airlines flight. United and Alaska are the two big U.S. carriers that fly Boeing jets with door plugs.
Officials say the business jet may have experienced problems with its stability before it hit roughness that caused the death Dana Hyde, a passenger who served in prominent posts for two presidents.
A wheel bearing on the train's 23rd car overheated to a dangerous degree, a new NTSB report says. An earlier warning may have helped to prevent the derailment, officials said.
