On their son Bryce's birthday this year, Silene Fredriksz-Hoogzand and her husband Rob went to a Dutch air base, watched pall bearers solemnly unload seven coffins from a military cargo plane and wondered if they contained parts of the remains of Bryce or his girlfriend Daisy Oehlers.

For many families of the 298 people killed when Malaysia Airlines Flight 17 was brought down July 17 last year over eastern Ukraine, uncertainty and agonizing waiting is still woven into the fabric of life a year later.

"Your world stops with a bang," Silene said at her home in Rotterdam, where flowers and mementos to Bryce and Daisy still dominate the living room. The couple's bedroom is still the same disorderly mess it was the day they left for a vacation to Bali. "Everything around you continues. You try to participate, but it's just hard."

As if waiting for remains of loved ones were not bad enough, families also still have not received conclusive answers to many questions about the crash: Who brought down the plane? Will the perpetrators ever face justice? Why was the Boeing 777 heading from Amsterdam to Kuala Lumpur even flying over a war zone?

International investigators say it will be October before they publish the official cause of the crash. A Dutch-led criminal investigation into the downing won't be done until the end of the year — adding to family frustrations.

"I understand their impatience. They want to know exactly what happened. They want answers," said Fred Westerbeke, the prosecutor leading the criminal probe. "Many big criminal investigations do take a lot of time and because of all the circumstances this investigation is not an easy one."

The criminal investigation is focusing on a BUK surface-to-air missile downing MH17 as the most likely scenario but is also working to rule out other possible causes. The Dutch Safety Board said in a preliminary report that the plane was hit by multiple high-energy objects, a conclusion experts said bears the hallmarks of a missile strike.

Ukraine blames Russian-backed separatist rebels, Moscow blames Ukraine. Countries who lost citizens in the disaster are trying to establish a United Nations tribunal to prosecute any suspects eventually identified.

Rob Fredriksz fears economic and geopolitical interests may be part of the delay.

"They're operating too carefully. A bit scared," he said. "I think it's politically too sensitive."

Along with the impatience, there is understanding from some relatives.

James Rizk, a 22-year-old real estate agent from the Australian city of Melbourne, is confident that the slow but methodical international investigations will eventually mean that the killers of his parents Albert and Maree Rizk will face justice.

"I've got confidence in our government. They're doing a good job and I believe they're on the right track at the moment," Rizk said. "It's just one of those things that can't happen overnight."

The disaster was a second and tragically familiar blow to the extended family in only four months. Maree Rizk's stepmother Kaylene Mann lost a brother Rod Burrows and sister-in-law Mary Burrows on Malaysia Airlines Flight 370, which is thought to have plunged in the Indian Ocean on March 8. That plane and all its 238 passengers and crew remain missing. The reasons for their disappearance are a mystery.

At least James Rizk did not have to wait too long for his parents' bodies to return home. They were the first of the 38 Australian permanent residents and citizens killed on Flight 17 to be repatriated, six weeks after MH17 was shot down.

Others have had a hard period of uncertainty. Evert van Zijtveld buried only partial remains of his 18-year-old son Robert-Jan and 19-year-old daughter Frederique in December.

"You can't keep saying 'I'm not going to do anything,'" he said. "We got something back — small as it was — so we gave it a place. The graveyard is close to our home."

But since the funeral, later Dutch missions to recover human remains from the scorched crash site in eastern Ukraine have returned with more fragments of the teenagers, confirmed through DNA analysis by a team that has, in the year since the crash, positively identified remains of all but two of the people killed on MH17.

Now "we don't know what to do. It's very difficult to take the decision to open the grave to add pieces of bone," Van Zijtveld said.

On Friday, families will gather again, as they did in the shocked days immediately after the disaster, and hold commemorations.

James Rizk is going to the Australian capital, Canberra, where lawmakers are interrupting their six-week mid-year break for a memorial that includes the unveiling of a plaque in the House of Representatives garden listing the names of all 298 victims.

The family will then fly from Canberra 480 kilometers (300 miles) to Melbourne for commemorations at their beloved Sunbury Football Club the following day. James Rizk plays at the Aussie rules football club, where his father was a committee member and his mother volunteered in the canteen. Albert and Maree Rizk will be remembered with a plaque on a grandstand to be built within the next year.

Families will also gather Friday in the Netherlands. Among them will be relatives of Malaysia Airlines flight attendant Dora Shahila Kassim, who will fly in from Kuala Lumpur.

Diyana Yazeera, Kassim's 16-year-old daughter, hugged a pillow and sobbed as she recalled growing up with her divorcee mother.

"She was not just my mother but my father, my best friend," she said at her family's home. "I don't know how I am going to live without her."

In Rotterdam, Silene and Rob take comfort from friends and family as the anniversary approaches, but the pain of their loss, if anything, is just getting worse.

"We're a year further, but actually we've made no progress," Rob said. "For us, every day is July 17."

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Associated Press writers Rod McGuirk in Canberra and Eileen Ng in Kuala Lumpur contributed.