A plane of United airlines takes off next to an Airbus A350-900 of Ethiopian Airlines at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

A plane of Germany's air carrier Lufthansa takes off at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

A plane of Germany's air carrier Lufthansa takes off at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The emergency door of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

A Rolls-Royce engine of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

Thomas Gabreyohannes, Director for Germany and Central Europe of Ethiopian Airlines walks down the gangway of an Airbus A350-900 during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The business class cabin of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The cockpit of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The cockpit of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The economy class cabin of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The business class cabin of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The kitchenette of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

PR agent Elsa Goette sits in a Rolls-Royce engine of an Airbus A350-900 of Ethiopian Airlines during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The cockpit of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The cockpit of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

The business class cabin of an Airbus A350-900 of Ethiopian Airlines is photographed during a site-inspection at Fraport airport in Frankfurt, Germany, May 22, 2017. REUTERS/Kai Pfaffenbach

A Philippine Airlines passenger jet is pictured at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

Air Asia passenger jet is pictured at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

A Cebu Pacific passenger jet taxis past a Philippine Airlines passenger jet at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

A security guard stands near Cebu Pacific passenger jets at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

AirAsia passenger jet is pictured at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

Cebu Pacific passenger jets are pictured at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

Cebu Pacific passenger jets are pictured at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

A Cebu Pacific passenger jet is pictured at the tarmac of Legazpi, Albay in central Philippines April 1, 2016. REUTERS/Erik De Castro

Ground crew walk past Cebu Pacific passenger jets at the tarmac of Terminal 3 at the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

A Cebu Pacific flight stewardess tells the passengers the location of oxygen masks in case of an emergency before take off at the Terminal 3 of the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro

A Cebu Pacific flight stewardess demonstrates how to use a life jacket to the passengers before take off at the Terminal 3 of the Ninoy Aquino International aiport in Pasay city, Metro Manila Philippines April 1, 2016. REUTERS/Erik De Castro