A man works on C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

Workers inspect a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man shines a torch as he inspects rivets on a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man shines a torch as he inspects rivets on a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

People work on a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A worker inspects a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man looks at paperwork on C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on C Series aeroplane wing in the pressure test area of Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

People work in the pressure test area on C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A worker inspects a C Series aeroplane wing that was assembled in the Bombardier factory in Belfast , Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on a C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A man works on C Series aeroplane wing in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

General view of people working on C Series aeroplane wings in the Bombardier factory in Belfast, Northern Ireland September 26, 2017. REUTERS/Clodagh Kilcoyne 

A Zipline delivery drone sits on a work bench at an undisclosed location during a flight demonstration in the San Francisco Bay Area, California, U.S., May 5, 2016. REUTERS/Stephen Lam 

A carbon fiber fuselage of a Zipline delivery drone sits on a work bench at an undisclosed location during a flight demonstration in the San Francisco Bay Area, California, U.S., May 5, 2016. REUTERS/Stephen Lam 

A Zipline delivery drone sits on a work bench at an undisclosed location during a flight demonstration in the San Francisco Bay Area, California, U.S., May 5, 2016. REUTERS/Stephen Lam 

A Boeing 737 MAX 8 sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

An engine of a Boeing 737 MAX is seen while the plane sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

A Boeing 737 MAX sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

A portion of a painted Boeing 737 MAX fuselage is seen while it sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

A Boeing 737 MAX 8 sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

A Boeing 737 MAX 8 sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

A Boeing 737 MAX 8 sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

A Boeing 737 MAX sits outside the hangar during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 8, 2015. REUTERS/Matt Mills McKnight 

A Boeing 737 MAX plane is seen during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

Boeing employees march up and down stairs entering and exiting Boeing 737 MAX during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

A Boeing 737 MAX is pictured during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

Boeing employee Mike Laeuger is seen working on Boeing 737 MAX during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

The interior of an unfinished Boeing 737 MAX is pictured during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

A wing of the Boeing 737 MAX is pictured during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

Boeing employee Mike Laeuger is seen working on Boeing 737 MAX during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

Visitors look at the Boeing 737 MAX production line during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

An employee is seen passing the nose of a Boeing 737 MAX during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

The cockpit is pictured during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

Boeing employees work on the tail of a Boeing 737 NG at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

Boeing employees work during a media tour of the Boeing 737 MAX at the Boeing plant in Renton, Washington December 7, 2015. Picture taken December 7, 2015. REUTERS/Matt Mills McKnight 

Chinese President Xi Jinping speaks after his tour of the Boeing assembly line in Everett, Washington September 23, 2015. REUTERS/Mark Ralston/Pool

Chinese President Xi Jinping (R) speaks beside Ray Conner (L), president and CEO of Boeing Commercial Airplanes, and Dennis Muilenburg (2nd L), president and CEO of the Boeing Company, after his tour of the Boeing assembly line in Everett, Washington September 23, 2015. REUTERS/Mark Ralston/Pool 

Chinese President Xi Jinping (R) speaks beside Ray Conner (L), president and CEO of Boeing Commercial Airplanes, and Dennis Muilenburg (2nd L), president and CEO of the Boeing Company, after his tour of the Boeing assembly line in Everett, Washington September 23, 2015. REUTERS/Mark Ralston/Pool TPX IMAGES OF THE DAY

Visitors look at models of Boeing aircrafts at the Aviation Expo China 2015, in Beijing, China, September 16, 2015. Boeing Co said on September 23, 2015 it had won orders and commitments from China for 250 narrowbody 737 aircraft and 50 widebody aircraft, valued at about $38 billion at list prices. Boeing also was due to announce later in the day an agreement to build a 737 completion center in China that would finish and deliver 737s built at Boeing's factory in Renton, Washington. Picture taken on September 16, 2015. REUTERS/Jason Lee 

Members of the Chinese delegation unload luggage from a Boeing 747-400 carrying Chinese President Xi Jinping and First Lady Peng Liyuan as motorcade vehicles stand by at Paine Field in Everett, Washington, September 22, 2015. Chinese President Xi Jinping will meet U.S. tech titans and tour Boeing Co's biggest factory and Microsoft Corp's sprawling campus near Seattle this week as he kicks off a U.S. visit that also includes a black-tie state dinner at the White House hosted by President Barack Obama. REUTERS/David Ryder 

A Boeing 747-400 carrying Chinese President Xi Jinping and First Lady Peng Liyuan arrives at Paine Field in Everett, Washington, September 22, 2015. Chinese President Xi Jinping will meet U.S. tech titans and tour Boeing Co's biggest factory and Microsoft Corp's sprawling campus near Seattle this week as he kicks off a U.S. visit that also includes a black-tie state dinner at the White House hosted by President Barack Obama. REUTERS/David Ryder 

A Boeing 747-400 carrying Chinese President Xi Jinping and First Lady Peng Liyuan arrives at Paine Field in Everett, Washington, September 22, 2015. Chinese President Xi Jinping will meet U.S. tech titans and tour Boeing Co's biggest factory and Microsoft Corp's sprawling campus near Seattle this week as he kicks off a U.S. visit that also includes a black-tie state dinner at the White House hosted by President Barack Obama. REUTERS/David Ryder 

Chinese President Xi Jinping and First Lady Peng Liyuan arrive at Paine Field in Everett, Washington, September 22, 2015. Chinese President Xi Jinping will meet U.S. tech titans and tour Boeing Co's biggest factory and Microsoft Corp's sprawling campus near Seattle this week as he kicks off a U.S. visit that also includes a black-tie state dinner at the White House hosted by President Barack Obama. REUTERS/David Ryder 

Andalusia's regional government president Susana Diaz (L) speaks during a news conference next to Fernando Alonso, head of Airbus flight testing and operations, in the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Andalusia's regional government president Susana Diaz smiles during her visit to the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Andalusia's regional government president Susana Diaz is seen during her visit to the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Andalusia's regional government president Susana Diaz smiles during her visit to the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Andalusia's regional government president Susana Diaz is seen during her visit to the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Andalusia's regional government president Susana Diaz (R) chats and poses with Fernando Alonso, head of Airbus flight testing and operations, during her visit to the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Andalusia's regional government president Susana Diaz smiles during her visit to the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Andalusia's regional government president Susana Diaz (L) walks next to Fernando Alonso, head of Airbus flight testing and operations, during her visit to the Airbus assembly plant in the Andalusian capital of Seville, southern Spain, September 14, 2015. REUTERS/Marcelo del Pozo

Bruno Trevidic of France photographs the Airbus A321 being assembled during a tour of the new Airbus U.S. Manufacturing Facility in Mobile, Alabama September 13, 2015. Airbus Group's new factory will build predominately A321 aircraft, the company's largest single aisle plane, Airbus Group's president and CEO Fabrice Bregier said on Sunday. Picture taken September 13, 2015. REUTERS/Michael Spooneybarger 

The delivery center at the new Airbus U.S. Manufacturing Facility in Mobile, Alabama September 13, 2015. Airbus Group's new factory will build predominately A321 aircraft, the company's largest single aisle plane, Airbus Group's president and CEO Fabrice Bregier said on Sunday. Picture taken September 13, 2015. REUTERS/Michael Spooneybarger 

People walk along the delivery center during a tour of the new Airbus U.S. Manufacturing Facility in Mobile, Alabama September 13, 2015. Airbus Group's new factory will build predominately A321 aircraft, the company's largest single aisle plane, Airbus Group's president and CEO Fabrice Bregier said on Sunday. Picture taken September 13, 2015. REUTERS/Michael Spooneybarger