Kuala Lumpur, Malaysia (CNN) -- The families of those on board Malaysia Airlines Flight 370 have been waiting for answers for 20 days. The loved ones of those who were passengers on Malaysia Airlines 653 have been waiting for 37 years.
Flight 653 was hijacked in 1977 en route from the northern Malaysian city of Penang to Kuala Lumpur, the country's capital. The airliner -- a Boeing 737-200 -- crashed into a mangrove swamp as it descended, killing all 100 on board. Before Flight 370, it was the deadliest incident in Malaysian aviation history.
"Thirty-seven years down the line, we still don't really know the truth," said Ruth Parr, who was 19 when her father, Thomas, died in the crash.
The hijacker or hijackers of MH653 have never been identified, despite cockpit voice recordings that captured everything from the breach of the cockpit, to the sound of gunshots that killed both pilots. According to the Malaysian Civil Aviation Department's report into the crash, the aircraft was hijacked as it approached Kuala Lumpur.
Amid confusion over whether it was to land there or not, it proceeded towards neighboring Singapore. As it descended, the crew was shot and the aircraft "carried out some unusual pitch up and pitch down terminal maneuvers before finally impacting into swampy ground at some 450 knots." The report concluded that the crash was caused by the crew being fatally incapacitated, leaving the aircraft "professionally uncontrolled."
However, some eye witnesses at the time reported seeing the aircraft in flames before it hit the ground, while others reported hearing an explosion before impact -- though investigators could not find evidence to support these reports.
For other family members of MH653 victims reached by CNN, the recent disappearance of MH370 brought back memories of that traumatic time. Over the years, they have learned to cope with their grief, but the 1977 crash will always be a defining event in their lives.
"You have to carry that with you all the time," said Tom Sherrington, whose father, Richard, was also on MH653. He believes talking openly about their memories of his father, whom he described as a "fun guy" and "big adventurer," helped his family to cope.
He also said visits to the memorial, built near the crash site in the Malaysian coastal town of Tanjung Kupang, have given his family a tangible place to reflect on their loss.
As for the families of those on board MH370, Sherrington said they should focus on remembering their loved ones and try not to fixate on assigning blame.
"The one thing I would say is not for them to get too obsessed with the detail and the recriminations and all that," he said. Sherrington added that he hopes the families will stick together and find comfort in each other.
'You can never forget the date'
Both Parr and Sherrington warn that everyone processes their grief in different ways and there is no shortcut.
It gets a little easier over time but you can never forget the date," Parr said.
"You will forever think you see that person out and about, a glance in the car's rearview mirror or crossing the road. It could be anywhere, a voice that sounds like him will have you spinning around only to find it's someone else."