(Bloomberg) -- Three crashes which have yet to be fullyexplained, involving the most modern airliners in the safest phaseof flight, made last year the deadliest for air travel in almost adecade.

The loss of two Malaysian Air Boeing Co. 777s, one thought tohave disappeared in the Indian Ocean, and flight MH17 presumed shotdown over Ukraine, plus last week’s unexplained AirAsia tragedy,killed 665 passengers, accounting for 75% of the annual toll of884, according to safety consultant Ascend Worldwide.

The run of mystery crashes, which began when Malaysian AirlineSystem Bhd. flight MH370 vanished on March 8 and ended with thedemise of AirAsia QZ8501 on a routine trip from Java to Singaporeon Dec. 28, meant 2014 was the most lethal year in civil aviationsince 2005, when 1,056 died, Ascend said. The number of fatalcrashes was unchanged, and the balance involved older turbopropsflying in emerging nations and conforming more closely to thetypical profile for accidents in recent years.

“Planes are becoming so big that the loss of even one wide-bodycan have a major impact on the data,” said Paul Hayes, head ofsafety at Ascend, who has tracked air-crash trends since 1974.“Factor out acts of violence and other anomalies and the industryis still getting safer, but if your relative was on MH17 it doesnot really matter how they died.”

Planes seating more than 14 people suffered 10 events thatkilled passengers last year, the same number as in 2013, when 220travelers died, and 2012, when 416 perished, Ascend said.

Cruising Height

The three major crashes were unusual because each involved amodern, western-built model, with the Boeing 777 wide-bodies thatoperated Malaysian Air flights MH370 and MH17 dating from 2002 and1997, respectively, and AirAsia’s lost Airbus Group NV A320narrow-body built only in 2008.

All three jets had also been flying at cruising altitude, withMH370 having leveled out at 35,000 feet after departing KualaLumpur for Beijing before doubling back over the Malay peninsulafor unexplained reasons. MH17 was operating at 33,000 feet when itplummeted to the ground, and QZ8501 was at 32,000 feet when itspilots asked to go higher in stormy weather.

The Netherlands-based Aviation Safety Network, which recorded 21fatal airliner accidents last year, including cargo flights, said13 crashes occurred in the en-route phase, versus three during boththe initial climb and landing approach. One deadly event happenedduring landing itself and none on takeoff.

Suicide Theory

By contrast, between 1959 and 2013, 47% of crashes and 40% ofdeaths came during landing, Malaysia-based Maybank said this weekafter the AirAsia loss, citing Boeing’s Statistical Summary of JetAirplane Accidents. The cruise phase accounted for only 10% ofcrashes, though survivability was lower, so that it produced 20% offatalities.

While full explanations have yet to be formulated for the threeworst incidents of 2014, safety experts have suggested thedisappearance of MH370 -- and its 227 passengers -- most likelyinvolved pilot malpractice, since all devices indicating theplane’s position were turned off. A search for debris and the 777’sblack-box flight recorders that might reveal the truth of itsdemise continues off Australia.

Malaysian Air flight MH17 was downed in a war zone in easternUkraine, killing all 283 passengers, after being hit by “a largenumber of high-energy objects,” the Dutch Safety Board said Sept.9. The board stopped short of laying the blame on a ground-to-airmissile strike, which the U.S. has said was most likely the causeand probably fired by pro-Russia rebels.

Stray Fire

The Dutch -- leading the investigation because more than 190victims were from the Netherlands -- cautioned that the probe is inits early stages, pledging only that a definitive study will comewithin one year of the July 17 tragedy.

Another incident classified with MH17 as non-accidental byAscend saw a woman die on a Pakistan International Airlines flightafter an Airbus A310 carrying 196 passengers came under fire,possibly by AK-47 assault rifles, while landing in Peshawar. Theincident came two weeks after a Taliban attack on Karachi airportkilled 36 people, though none were on aircraft.

Excluding “acts of violence,” the 2014 death-toll would havebeen 600, the highest since 2010’s 822, Ascend said.

In the AirAsia crash, which killed 155 passengers and involvedan experienced pilot who failed to transmit a distress signal, it’spossible weather played a key role. The jet appears to have flowninto a storm cloud where its engines could have been affected byice formation, researchers from the Indonesian meteorologicaloffice said in a report citing data from the jet’s last knownlocation.

Tropical Storm

Among other events in 2014, the worst involved the loss of aMcDonnell Douglas MD-83 jet flying for Air Algerie in Mali on July24, killing 110 travelers, and a TransAsia Airways Corp. ATR-72crash in Taiwan a day earlier, with 44 passenger deaths.

Weather was a factor in both cases, with the MD-83 crewencountering a storm about 40 minutes after takeoff and the ATRturboprop destroyed on a second runway approach amid heavy rainfrom tropical storm Matmo. Some 15 travelers also died when a NepalAirlines de Havilland Canada DHC-6 Twin Otter turboprop hit jungleon a 7,000-foot hillside in poor weather on Feb. 16.

A crash that killed 42 people in Iran in August came after thecountry sought to develop its own aerospace industry to escape theimpact of western sanctions. The government later grounded theIran-140 turboprop to determine whether a spate of accidents couldbe traced to faults intrinsic to the plane.

The two other fatal events concerned a Twin Otter that hit amountain in Papua New Guinea in poor visibility in September and aRussian-built Antonov An-26 that crashed in Tunisia after flyingfrom Libya in February. Both models are turboprops.

About 100,000 flights a day land without incident worldwide, theInternational Air Transport Association says. In 2013, passengertrips on airlines exceeded 3 billion.

--With assistance from Andrea Rothman in Toulouse andKyunghee Park in Singapore.

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