Allen Cates Books and Articles

When Air America Captains Terry D. Clark, Charles L. Osterman, Hank De Voll, Mark Hotchkiss, and Flight Mechanic Valeriano P. Rosales launched from Hue, Vietnam, bound for La Boa via Quang Tri, they had every reason to believe it would be a routine mission.

In 1973, Air America, Inc., a federally owned company, contracted with the International Control and Supervision (ICCS), a multinational organization tasked with overseeing the ceasefire and ensuring compliance with the Paris Peace Accords.

In early April 1973, poor weather grounded nearly all flying in I Corps. When conditions finally improved, the mission was launched. About 10 minutes from their destination, Clark and Osterman's helicopter was hit by an SA-7 heat-seeking missile and destroyed in midair, tragically killing the crew and eight passengers, including two North Vietnamese.

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The official account of the incident states:

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 “On April 7, 1973, an Air America Bell UH-1H helicopter (tail number 17006) contracted to the International Commission of Control and Supervision (ICCS) was shot down by a North Vietnamese SA-7 shoulder-fired missile. The unarmed, visibly marked aircraft was on a pre-arranged flight path near Huong Hoa (west of Khe Sanh). All nine people aboard—two American civilians, one Filipino crew member, one Canadian, two Hungarians, one Indonesian, and two Viet Cong liaison officers—were killed.

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The other helicopter, operated by Mark Hotchkiss and Hank Devoll, was hit by ground fire and forced down, but the crew survived.”

They were captured and held as POWs for 36 hours. It should never have happened.

The North Vietnamese resorted to unjust coercion, forcing the crew of the second helicopter into signing a document stating they were off course, justifying the North Vietnamese actions.

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The ICCS personnel were there to enforce the truce. Air America may have contracted with ICCS, but it remained a company federally owned by the U.S. government.

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ICCS personnel on board the second helicopter verified that the helicopters were on the proper course. The attack was unprovoked, and, despite eyewitness testimony from ICCS personnel confirming the helicopters were on the proper flight path, no formal response came from the U.S. government. Adding insult to injury, Saigon's helicopter flight crews were ordered to take navigation training even though most had been working in Vietnam for several years.

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The crews attended the class begrudgingly, knowing they had not been at fault and believing their government had failed to support them.

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The surviving flight crew gave an interview recorded by the Miami Herald. "During the period, there were 18,000 alleged ceasefire violations, which resulted in over 76,000 killed, wounded, and missing on both sides: on May 29th, 1973, the Canadians announced that they were withdrawing from the ICCS because they had come to supervise a ceasefire but were instead observing a war."

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This assessment is supported by William Le Gro in Vietnam from Cease-Fire to Capitulation and by the official Canadian government history of the ICCS, which explains Canada's decision to withdraw and the circumstances surrounding it.

Richard Nixon wrote:

 

“When we signed the peace agreements of 1973, we had won the war. We then proceeded to lose the peace. The South Vietnamese successfully countered Communist violations of the cease-fire for two years. Defeat came only when Congress, ignoring the specific terms of the peace agreement, refused to provide military aid to Saigon equal to what the Soviet Union provided to Hanoi”

 

The historical record is clear. North Vietnam repeatedly violated the ceasefire, and the United States ultimately chose not to respond militarily. Much has been written about the political reasons for that decision. Far less has been written about the men of Air America who continued to fly under those conditions and paid the price.

 

When Air America’s mission ended, its employees were simply told to go home. There were no victory parades, no public recognition, no official acknowledgment of what they had endured, and little appreciation for the sacrifices they and their families had made.

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The war continued after April 1973 and didn't fully end until 1975. Once again, Air America was called upon during Operation Frequent Wind, where tragedies were commonplace, yet the sacrifices of those who served remained largely unrecognized.

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The photographs and Air America document that accompany this article were provided by Rose De Voll, the wife of the late Hank De Voll, whose commitment to preserving this history has ensured that these events will not be forgotten.

 

Allen Cates

Former Air America Pilot

Author

Honor Denied

Above the Rice

The Girl with a Silver Necklace

Integrity’s Conundrum

The Uncertainty Protocol

www.allenCates.com

Copyright © 2026 Allen Cates. All Rights Reserved.

Sources

• Le Gro, William. Vietnam from Cease-Fire to Capitulation.

• Government of Canada. History of the International Commission of Control and Supervision (ICCS).

• Nixon, Richard. No More Vietnams.

• Miami Herald interview with surviving Air America crew.

• Air America Association Archives.

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