Aviation safety and security

Ground crew chat near a Boeing 737 MAX 8 plane operated by Shanghai Airlines parked on tarmac at Hongqiao airport in Shanghai, China, Tuesday, March 12, 2019. U.S. aviation experts on Tuesday joined the investigation into the crash of an Ethiopian Airlines jetliner that killed 157 people, as a growing number of airlines grounded the new Boeing plane involved in the crash. (AP Photo)

Rescuers work at the scene of an Ethiopian Airlines flight crash near Bishoftu, or Debre Zeit, south of Addis Ababa, Ethiopia, Monday, March 11, 2019. A spokesman says Ethiopian Airlines has grounded all its Boeing 737 Max 8 aircraft as a safety precaution, following the crash of one of its planes in which 157 people were killed. (AP Photo/Mulugeta Ayene)

In this Dec. 15, 2018, photo released by Xinhua News Agency, invited guests take photos of the Boeing 737 Max 8 airplane deliver to Air China during a ceremony at Boeing Zhoushan 737 Completion and Delivery Center in Zhoushan, east China's Zhejiang Province. China's civilian aviation authority has ordered all Chinese airlines to ground their Boeing 737 Max 8 planes on Monday, March 11, 2019 after one of the aircraft crashed in Ethiopia. The authority said the one-day action was made out of safety concerns because the crash was similar to one in Indonesia last year. (Xu Yu/Xinhua via AP)

In this Dec. 15, 2018, photo released by Xinhua News Agency, invited guests take photos of the Boeing 737 Max 8 airplane deliver to Air China during a ceremony at Boeing Zhoushan 737 Completion and Delivery Center in Zhoushan, east China's Zhejiang Province. China's civilian aviation authority has ordered all Chinese airlines to ground their Boeing 737 Max 8 planes on Monday, March 11, 2019 after one of the aircraft crashed in Ethiopia. The authority said the one-day action was made out of safety concerns because the crash was similar to one in Indonesia last year. (Xu Yu/Xinhua via AP)

Members of the Ethiopian community take part in a special prayer for the victims of the Ethiopian Airlines flight ET302 crash, at the Ethiopian Orthodox Tewahedo Church of Canada Saint Mary Cathedral in Toronto, on Sunday, March 10, 2019. Ethiopian Airlines flight ET302 crashed shortly after takeoff from Ethiopia's capital on Sunday morning, killing all 157 on board, authorities said, including 18 Canadians. (Christopher Katsarov/The Canadian Press via AP)

FILE - In this Oct. 4, 2017, file photo, SilkAir's new Boeing 737 Max 8 aircraft is seen through a viewing gallery window parked on the tarmac of Singapore's Changi International Airport. China's civilian aviation authority has ordered all Chinese airlines to temporarily ground their Boeing 737 Max 8 planes after one of the aircraft crashed in Ethiopia. The Civil Aviation Administration of China said the order was issued at 9 a.m. Beijing time Monday, March 11, 2019 and would last nine hours. (AP Photo/Wong Maye-E, File)

This photo provided by the Transportation Security Administration shows a defunct grenade launcher that TSA agents spotted in a passenger’s checked bag at Lehigh Valley Airport in Allentown, Pa The TSA says the unassembled parts of the launcher and a replica grenade were found on Monday, March 4, 2019, when an alarm went off as the bag passed through security equipment at the airport, about 60 miles (96 kilometers ) north of Philadelphia. The man, from St. Augustine, Fla., was stopped by police and told officials he thought he could bring the non-functioning launcher onboard in a checked bag. (Transportation Security Administration via AP)