PORTLAND, Maine — Almost 60 decades ago, dozens of soldiers assembled to get a top secret assignment to Vietnam, three years prior to President Lyndon Johnson officially sent U.S. combat troops to the country.

They never made it. Their plane disappeared between Guam and the Philippines, leaving behind no trace.

Ever since, their families have been struggling to get answers about the mission from the Pentagon. They also want their loved ones to be recognized on the Vietnam Veterans Memorial in Washington, D.C.

For those families, it has been heart-wrenching that the soldiers were not properly memorialized like others who died in the war.

“I really do feel frustrated. It is almost like they never existed since soldiers.

On Saturday, families of more than 20 of those fallen soldiers were on hand for the unveiling of a memorial in Columbia Falls, Maine, to honor those who perished when the plane disappeared over the Pacific Ocean. Columbia Falls is approximately 190 miles (305 kilometers) northeast of Portland, Maine.

“It’s incredible,” said Donna Ellis, of Haslett, Michigan, who was 5 when her dad, Melvin Lewis Hatt, died in the crash.

The assignment, early in the Vietnam war, is shrouded in mystery.

Soldiers from across the country assembled at Travis Air Force Base in California prior to boarding a propeller-powered Lockheed Super Constellation operated by the Flying Tiger Line, which chartered flights for the U.S. military.

The 93 U.S. soldiers, three South Vietnamese and 11 crew members aboard Flight 739 never made it to Saigon. It departed from California and made refueling stops in Hawaii, Wake Island and Guam before vanishing on another leg of this flight to the Philippines on March 16, 1962.

There was a report of a midair explosion observed by sailors on a tanker in the region, but no debris from the aircraft was recovered.

The families have spent years seeking answers to no avail. Freedom of Information Act requests by Ellis and many others yielded redacted files with little useful information about the covert assignment.

“It turns into a rat maze,” Ellis explained.

Since their deaths weren’t in the combat zone, their titles weren’t allowed on the Vietnam Veterans Memorial in Washington.

“It’s past time that we properly honor those missing. That is why I will keep working with my coworkers and also the families of those lives lost on ways we could honor the servicemembers,” Peters said.

In Maine, the creator of Wreaths Around America, which places wreaths in Arlington National Cemetery and at seasoned gravesites across the world, was moved from the story and decided to make a monument. The granite stone has a marble marker with all the names on it.

The unveiling Saturday featured a reading of the titles, a rifle salute, the playing of taps as well as the placing of a wreath.

Phil Waite by the United States of America Vietnam War Commemoration told the group he considers that the ministry reflects”a first step” to greater recognition. “I think there’s more to come,” he explained.

The occasion provided an opportunity for families to get together and share stories.

“This will be closure for a whole lot of households,” explained Susie Linale, of Omaha, Nebraska, part of a contingent of six family members, including her sister and sister. They wore buttons using a picture of their father, Albert Francis Williams Jr., who died in the crash.