2017 was a spotless year for commercial travel, so why has 2018 started off so badly?
Air safety in 2018: should we be concerned about flying?
Almost 200 people have been killed in a spate of passenger plane crashes in the first three months of this year, after a fatality-free 2017 for commercial jets.
While it's impossible to draw comparisons to any of the recent aviation accidents, questions have naturally resurfaced over air safety and why it's been such a bad start to 2018 for flying.
It's not easy coming off the back of what seems like an anomaly for the industry: a year without a single commercial passenger jet fatality, making it the safest on record for commercial air travel.
But does the question need to be posed? Is air safety suddenly regressing?
Luckily, the answer seems to be no. Air travel remains the safest mode of transport in the world, and aviation experts are quick to put paid to any comparisons between separate crashes.
By the numbers
Since January, there have been four major commercial jet crashes, with 196 people killed between them. That number might have doubled had the year's first crash resulted in fatalities.
- January 13: Pegasus Airlines Flight 8622 skidded off the end of the runway at Trabzon Airport, Turkey and came to rest on a cliff. All 168 passengers and crew survived without any injuries, and instead the most notable thing to come out of the potential disaster was a spectacular picture which quickly went viral.
- February 11: Saratov Airlines Flight 703, crashed shortly after take-off from Domodedovo International Airport in Russia. All 71 passengers and crew were killed.
- February 18: Iran Aseman Airlines Flight 3704 crashed into the Zagros Mountains in Iran, killing all 60 passengers, two security guards, two flight attendants and a pilot and co-pilot.
- March 12: US-Bangla Airlines Flight 211, on an international flight from Dhaka to Nepal, crashed at Tribhuvan International Airport, Kathmandu. At least 49 people, of the 71 onboard, died.
This only refers to aircraft that weigh over 5700kg, which is an International Civil Aviation Organisation (ICAO) weight-defined limit.
But there have also been a number of smaller crashes, which resulted in many fatalities. Not least Sunday's crash, which killed wealthy Turkish socialite and business heir Mina Basaran, 28, her seven friends and three crew members when a private plane travelling from Sharjah to Istanbul crashed in Iran.
On March 6, a Russian transport plane crashed in Syria, killing all 32 people on board, and on March 12, a helicopter carrying six people crashed in New York City's East River, killing all passengers, while the pilot survived.
What's behind the string of accidents?
Capt Darren Straker, former Chief Air Accident Investigator at UAE's General Civil Aviation Authority (GCAA) and independent investigator at Straker System Safety, claimed there was a common theme in some of the commercial airline crashes: an "attributable cause based on human error".
"A bad start to the year? Yes, but I think last year was the aberration, the system is now back to accidents and operational liabilities," he said.
"Despite the ICAO accident data trend decreasing for several years, the alarming increase in accidents where no technical cause has been prioritised, indicates that that the systemic underlying causes are still prevalent in accident causation."
The Pegasus Airlines flight was likely an engine or thrust problem, he said, and the Saratov Airlines flight had been caused by ice covering the speed sensors as the heaters were not turned on, despite it being the middle of winter.
The Iran Aseman Airlines, and US-Bangla crash were also avoidable, Mr Straker said.
On Monday, US-Bangla's chief executive Imran Asif said there had been a "fumble from the control tower" as the plane approached the airport's single runway.
Recordings of the conversation between air traffic control and the pilot appear to indicate confusion over which end of Kathmandu airport's single runway the plane was to approach.
"Kathmandu, well Nepal as a country, is on the ICAO blacklist as it has failed so many audits - it cannot recover without significant investment in infrastructure," Mr Straker said.
"A renewed and dedicated effort inline with the ICAO initiative 'No country left behind' can bring support and much needed expertise to countries without the effective infrastructure to support a fully enabled safety investigation process, increasing regional safety and oversight in regions where infrastructure and expertise are at a premium."
However, Saj Ahmad, chief analyst at StrategicAero Research, said it was "totally wrong to wonder why one year has had successive incidents and previous years may not have had any".
"Equally, it's unfair and irresponsible to try and connect [the crashes] in any way at all either and air transport remains by far and away the single most safest method of travel in the world".
He said pilots regularly trained for different scenarios, and accidents happened in unknown quantities. The flight paths from the UAE to Turkey, over Iran, are well-used as the most efficient air corridor for that region, he said, and also helped to avoid airspace around Iraq and Syria.
"Human error is always possible, and it has happened in various crashes - but the events of 2018 are still under investigation and nothing is clear about any of the crashes yet let alone pilot error being a factor," Mr Ahmad said.