Two military transport planes carrying 40 coffins bearing victims of the downed Malaysia Airlines Flight 17 landed Wednesday in the southern city of Eindhoven, and pro-Russian rebels shot down two fighter jets in Ukraine's restive east as fighting flared in the region.

Six days after the Boeing 777 was shot down over the battlefields of eastern Ukraine, the first bodies finally arrived in the Netherlands, the country that bore the heaviest toll in the crash that killed all 298 passengers and crew.

A Dutch Hercules C-130 that Dutch government spokesman Lodewijk Hekking said was carrying 16 coffins touched down first, closely followed by an Australian C-17 Globemaster plane carrying 24 coffins.

British investigators began work on a pair of "black boxes" to retrieve data on the flight's last minutes, while Dutch officials said they have taken charge of the stalled investigation of the airline disaster and pleaded for unhindered access to the wreckage.

The Dutch and Australian military transport planes departed Ukraine at midday, and landed at Eindhoven Air Base where the flights were met by Dutch King Willem-Alexander, Queen Maxima, Prime Minister Mark Rutte and other government officials. Hundreds of relatives were also there, Hekking said.

"If I have to wait five months for identification, I can do it," said Silene Fredriksz-Hoogzand, whose son, Bryce, and his girlfriend Daisy Oehlers died in the crash. "Waiting while the bodies were in the field and in the train was a nightmare."

King Willem-Alexander clasped his wife's hand as the couple grimly watched teams carry the coffins slowly from the planes to a fleet of waiting hearses. Almost the only sound was of boots marching across the ground and flags flapping in the wind.

From the airport, they were to be driven under military police escort to the central city of Hilversum where forensic experts were waiting at a military barracks to carry out the painstaking task of identifying the remains. Rutte says many bodies could be identified quickly and returned to their loved ones, but some families may have to wait weeks for a positive identification.

The bodies arrived back in the Netherlands - which is home to 193 of the victims - on a day of national mourning. Flags flew at half-staff on government buildings and family homes around this country of 17 million. Church bells rang out as the planes taxied to a standstill in Eindhoven.

Ukraine and Western nations are pressing the pro-Russian rebels who control the crash site to allow an unfettered investigation, something Russian President Vladimir Putin said he would use his influence to achieve. Though confident that a missile brought down the passenger jet, U.S. officials say Russia's role remains unclear.

Ukraine's defense ministry said two fighter planes were shot down about 20 miles south of the site of the Malaysia Airlines wreckage. The separatist group Donetsk People's Republic said in a statement on its website that one of the pilots was killed and another was being sought by rebel fighters.

While the insurgents deny having missiles capable of hitting a jetliner at cruising altitude, rebel leader Alexander Borodai has said that separatist fighters do have Strela-10M ground-to-air missiles which are capable of hitting targets up to an altitude of 11,500 feet.

In fighting on the ground Wednesday, rebel leader Pavel Gubarev wrote on his Facebook page that his men retreated Wednesday from the villages of Chervona Zorya and Kozhevnya, on the Russian border about 30 miles from the scene of the crash. Gubarev said 30 rebels had been injured.

Britain's Air Accidents Investigation Branch said Wednesday that Dutch authorities had delivered the plane's voice and data recorders to the agency's base at Farnborough, southern England, where information will be downloaded. Experts will also check for signs of tampering.

The Dutch Safety Board, which is leading an international team of 24 investigators, said unhindered access to the crash site was critical.

Spokesman Tjibbe Joustra told The Associated Press in a telephone interview that around 25 investigators already are in Kiev analyzing information including photos, satellite images and radar information, but have not yet gained access to the crash site.

"We haven't yet gotten guarantees about security for our way of working. If we go we have to be able to move freely," he said. "We hope to be able to get to the site soon."

Independent military analysts said Wednesday that the size, spread, shape and number of shrapnel impacts visible in an AP photograph of a piece of the wreckage all point to a missile system like the SA-11 Buk.

U.S. analysts have also concluded that an SA-11 was the likely weapon.

Konrad Muzyka, Europe and CIS armed forces analyst at IHS Jane's, said the high number of shrapnel holes in the debris meant that only a fragmentary warhead like the SA-11 could have been used. "The Buk has a 155-pound warhead which explodes and sends shrapnel out," he said. The fact the shrapnel holes are folded inwards confirmed that the explosion came from outside the plane, he added.

Justin Bronk, military sciences research analyst at the Royal United Services Institute, said "the size of shrapnel holes is fairly broad, in keeping with what you would expect from a large missile like the SA-11."