A Government Flying Services (GFS) Airbus H175 helicopter takes part in an anti-terrorist drill during an open day to mark National Security Education Day, at Hong Kong Police College, in Hong Kong, China April 15, 2021. REUTERS/Tyrone Siu

Yair Lapid, leader of Yesh Atid party, speaks to a youth during a visit to "Tom and Tomer Hill", a memorial site honouring the 73 soldiers who perished in the 1997 Israeli helicopter disaster, on Israel's Memorial Day, which commemorates fallen soldiers of Israel's wars and Israeli victims of hostile attacks, at Kibbutz Negba in southern Israel April 14, 2021. REUTERS/Amir Cohen

Yair Lapid, leader of Yesh Atid party, poses for a picture during a visit to "Tom and Tomer Hill", a memorial site honouring the 73 soldiers who perished in the 1997 Israeli helicopter disaster, on Israel's Memorial Day, which commemorates fallen soldiers of Israel's wars and Israeli victims of hostile attacks, at Kibbutz Negba in southern Israel April 14, 2021. REUTERS/Amir Cohen

People stand still as a two-minute siren marking Israel's Memorial Day, which commemorates fallen soldiers of Israel's wars and Israeli victims of hostile attacks, is heard, at "Tom and Tomer Hill", a memorial site, honouring the 73 soldiers who perished in the 1997 Israeli helicopter disaster, at Kibbutz Negba in southern Israel April 14, 2021. REUTERS/Amir Cohen

A stone bearing the Hebrew words, "In our hearts forever" is seen on the ground on Israel's Memorial Day, which commemorates fallen soldiers of Israel's wars and Israeli victims of hostile attacks, is heard, at "Tom and Tomer Hill", a memorial site, honouring the 73 soldiers who perished in the 1997 Israeli helicopter disaster, at Kibbutz Negba in southern Israel April 14, 2021. REUTERS/Amir Cohen

A woman and her children stand still as a two-minute siren marking Israel's Memorial Day, which commemorates fallen soldiers of Israel's wars and Israeli victims of hostile attacks, is heard, at "Tom and Tomer Hill", a memorial site, honouring the 73 soldiers who perished in the 1997 Israeli helicopter disaster, at Kibbutz Negba in southern Israel April 14, 2021. REUTERS/Amir Cohen

A helicopter drops water on a forest fire at Shivapuri National Park overlooking Kathmandu, as forest fires have raged many areas in Nepal contributing to worst air quality in the bowl shaped Kathmandu, Nepal April 11, 2021. REUTERS/Navesh Chitrakar

A military helicopter flies with Iraqi special forces soldiers hanging onto a rope and displaying Iraqi flags in Baghdad, Iraq April 6, 2021. REUTERS/Khalid al-Mousily

A helicopter drops water on a wildfire at the Sierra de Santiago, on the outskirts of Monterrey, Mexico March 29, 2021. REUTERS/Daniel Becerril

An undated handout picture shows Czech billionaire Petr Kellner, who was killed in a helicopter crash in Alaska, posing for a photograph. PPF Group/Handout via REUTERS

A helicopter flies just before curfew above South Beach during Spring Break in Miami, Florida, U.S., March 25, 2021. REUTERS/Yana Paskova

A Chinook helicopter flies over the city centre as people watch from a hotel balcony during a military parade marking the 200th anniversary of the Greek War of Independence, in Athens, Greece March 25, 2021. Kostas Tsironis/Pool via REUTERS

A helicopter flies over Athens during a military parade marking the 200th anniversary of the Greek War of Independence, in Athens, Greece March 25, 2021. REUTERS/Alkis Konstantinidis

A helicopter flies over Athens during a military parade marking the 200th anniversary of the Greek War of Independence, in Athens, Greece March 25, 2021. REUTERS/Alkis Konstantinidis

A helicopter flies over Athens during a military parade marking the 200th anniversary of the Greek War of Independence, in Athens, Greece March 25, 2021. REUTERS/Alkis Konstantinidis

Helicopters fly over Syntagma square during a military parade marking the 200th anniversary of the Greek War of Independence, in Athens, Greece March 25, 2021. REUTERS/Alkis Konstantinidis

A military helicopter flies past the Parthenon temple atop the Acropolis during celebrations for the 200th anniversary of the Greek War of Independence in Athens, Greece March 25, 2021. REUTERS/Costas Baltas

A military helicopter flies over the Parthenon temple atop the Acropolis during celebrations for the 200th anniversary of the Greek War of Independence in Athens, Greece March 25, 2021. REUTERS/Costas Baltas

Military helicopters fly over the Parthenon temple atop the Acropolis during celebrations for the 200th anniversary of the Greek War of Independence in Athens, Greece March 25, 2021. REUTERS/Costas Baltas

Military helicopters fly over the Parthenon during celebrations for the 200th anniversary of the Greek War of Independence in Athens, Greece March 25, 2021. REUTERS/Costas Baltas TPX IMAGES OF THE DAY

Military helicopters fly over the Parthenon during celebrations for the 200th anniversary of the Greek War of Independence in Athens, Greece March 25, 2021. REUTERS/Costas Baltas

Submerged houses are seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Flood affected areas are seen from a helicopter in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Australian Prime Minister Scott Morrison gets off a helicopter after an aerial tour of flood affected areas in Windsor and Pitt Town near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Australian Prime Minister Scott Morrison gets off a helicopter after an aerial tour of flood affected areas in Windsor and Pitt Town near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Submerged houses are seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

The roof of a submerged structure is seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Flood affected areas are seen from a helicopter in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

The roof of a submerged structure is seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

A partly submerged house is seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Flood affected areas are seen from a helicopter in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Flood affected areas are seen from a helicopter in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Flood affected areas are seen from a helicopter in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Australian Prime Minister Scott Morrison inspects damage created by floodwater from a helicopter during a visit to flood affected areas in Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Australian Prime Minister Scott Morrison inspects damage created by floodwater from a helicopter during a visit to flood affected areas in Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Partly submerged houses are seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Submerged houses are seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

A power pole surrounded by floodwater is seen from a helicopter in flood affected areas in the Windsor and Pitt Town areas along the Hawkesbury River near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Flood affected areas are seen from a helicopter in the Windsor area near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Australian Prime Minister Scott Morrison inspects damage created by floodwaters from a helicopter during a visit to flood affected areas in Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Australian Prime Minister Scott Morrison inspects damage created by floodwaters from a helicopter during a visit to flood affected areas in Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

Flood affected areas are seen from a helicopter in the Windsor area near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS TPX IMAGES OF THE DAY

Australian Prime Minister Scott Morrison inspects damage created by floodwaters from a helicopter during a visit to flood affected areas in Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS REFILE - QUALITY REPEAT

Flood affected areas are seen from a helicopter in the Windsor area near Sydney, Australia, March 24, 2021. Lukas Coch/Pool via REUTERS

A helicopter drops water on a wildfire at the Sierra de Santiago, on the outskirts of Monterrey, Mexico March 20, 2021. Picture taken March 20, 2021. REUTERS/Daniel Becerril

A helicopter make drops of water on a wildfire at the Sierra de Santiago, on the outskirts of Monterrey, Mexico March 20, 2021. REUTERS/Daniel Becerril

A helicopter carries a bucket of water to make drops on a wildfire at the Sierra de Santiago, on the outskirts of Monterrey, Mexico March 20, 2021. REUTERS/Daniel Becerril TPX IMAGES OF THE DAY

An helicopter used to extinguish a wildfire, flies back to an improvise base to be reloaded with water, at the Sierra de Arteaga, on the outskirts of Saltillo, Mexico March 17, 2021. REUTERS/Daniel Becerril

An helicopter flies near a devastated mountainous area due a fire at the Sierra de Arteaga, on the outskirts of Saltillo, Mexico March 17, 2021. REUTERS/Daniel Becerril

An helicopter flies through smoke during a wildfire that devastated some houses at the Sierra de Arteaga, on the outskirts of Saltillo, Mexico March 17, 2021. REUTERS/Daniel Becerril

A Department of Homeland Security helicopter flies above before House Minority Leader Kevin McCarthy and his delegation of Republican lawmakers hold a press conference on the US-Mexico border, in El Paso, Texas, U.S. March 15, 2021. REUTERS/Paul Ratje

A police officer keeps watch from a helicopter during a protest outside the University of Johannesburg during a nationwide shutdown of public universities in Johannesburg, South Africa, March 15, 2021. REUTERS/ Sumaya Hisham

A French SAMU rescue team helicopter lands at Angers hospital heliport with a patient suffering from the coronavirus disease (COVID-19) during his transfer from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe

A medical crew from Angers hospital loads a patient suffering from the coronavirus disease (COVID-19) on a stretcher after his transfer by a helicopter of French SAMU rescue team, from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe

A French SAMU rescue team helicopter lands at Angers hospital heliport with a patient suffering from the coronavirus disease (COVID-19) during his transfer from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe

A medical crew from Angers hospital carries a patient suffering from the coronavirus disease (COVID-19) on a stretcher after his transfer by a helicopter of French SAMU rescue team, from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe

A medical crew from Angers hospital loads a patient suffering from the coronavirus disease (COVID-19) on a stretcher after his transfer by a helicopter of French SAMU rescue team, from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe

A medical crew from Angers hospital carries a patient suffering from the coronavirus disease (COVID-19) on a stretcher after his transfer by a helicopter of French SAMU rescue team, from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe

A French SAMU rescue team helicopter lands at Angers hospital heliport with a patient suffering from the coronavirus disease (COVID-19) during his transfer from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe

A medical crew from Angers hospital load a patient suffering from the coronavirus disease (COVID-19) on a stretcher after his transfer by a helicopter of French SAMU rescue team, from the Ile de France region to Angers hospital, France, March 15, 2021. REUTERS/Stephane Mahe