In 1964 the CIA setup the 20th ASTA (later the 131st Aviation Company) and made it a MACV asset, outside of the normal I - IV Corps structure that had the other unarmed Mohawk units. While based near Hue in South Vietnam (I Corps, just below the DMZ), we flew entirely in Laos and North Vietnam for over seven years until the last months of the war. Our secondary base for over six years was Udorn RTAFB, Thailand where we flew nightly hunter/killer teams with the Air Force and Laotian forces attacking Chinese trucks and tanks across northern Laos, near (or sometimes across) the border far to the northwest of Hanoi. This was the war in the Plain of Jars (PDJ) and much of this was run from the secret CIA airfield at Long Teign (Lima Site-20a), the most secret airfield in the world and home to much of the Air America fleet.
Our two dozen Grumman OV-1 Mohawks were the only armed ones, and of the five Army Mohawk units, the other four operating only in South Vietnam, the 131st lost more aircraft and men than all the other units - combined.
Nightly, from Phu Bai we flew pairs of SLAR/IR hunter/killer teams in southern Laos (Steel Tiger North and South) with the AC-130 Spectre gunships attacking the Ho Chi Minh Trail around the clock. There we faced huge amounts of flak and other heavy anti-aircraft fire that were not an issue inside of South Vietnam.
We ran SLAR, IR and VR (armed visual) missions around the clock in the southern ends of North Vietnam, including 24/7 SLAR missions right along the coast up to about Vinh. There the issue was Soviet SAM missiles, and flak and the rest of the heavy machine guns. Ditto for Laos.
And we never got a single man back out of Laos at the end of the war. You go down in Laos - and you are gone for good.