There is still uncertainly for the Alexander C. R. Ducats of Bethesda who were told by the Air Force Thursday that the remains of their son Lt. Bruce C. Ducat, would be among those of 12 American servicemen to be turned over to a U.S. delegation in Hanoi.

The Ducats said yesterday they had been waiting 10 years, three months and 16 days to be certain whether their son, who was 25 when he was shot down over North Vietnan on Dec. 2, 1966, was alive or dead.

They are still waiting. "Until the remains have been properly identified, we just don't konw. We can't say anything," said Alexander Ducat.

Positive identification of the remains turned over yesterday to the five-member American delegation in Hanoi won't be made until next week after the dozen steel coffins are flown back to the United States.

Last Labor Day, Vietnamese Officials included Lt. Ducat's name in the list of 12 American servicemen who they said had died in North Vietnam.

That news was " a big disappointment, to say the least," said Ducat's father, a retired specialist in technical education who has served as an officer in the state chapter of the League of Families.

Until then, he said, although they had received no definite word, they believed their son to be alive.

"When he was hit, other pilots saw him and his copilot safely eject," Ducat said. He said his son's copilot, Col. Donald R. Burns, "said Bruce reached the ground safely, so we know he was alive when he was captured."

Col. Burns, who was released from a prisoner-of-war camp in 1973, never saw Bruce Ducat again. Ducat said, because North Vietnamese officals customarily placed captured pilots from the same unit in different POW camps.

Ducat, 74, said other servicemen saw his son's gear at one POW camp. The men never saw Bruce Ducat himself, however, nor was there ever any confirmation that the letters and packages from his wife and parents ever reached him.

In 1969 three American servicemen released by North Vietnam told Lt. Ducat's wife, who lives in Alamogordo, N.M., with their 11-year-old daughter that her husband was being kept prisoner in North Vietnam.

In 1970 Ducat went to Paris during the Vietnam peace talks and offered to exchange himself for his son. Ducat offered to help the North Vietnamese set up technical education programs.

"I have completed a satisfying career and my life is approaching its twilight," Ducat said at the time. "The greatest happiness I could have in the declining years of my life would be to have (my son) reunited with his wife and child."

Ducat never received a reply from North Vietnamese officials.

When asked about the toll the decade of waiting has taken on him and his wife, Ducat replied, "We're only one of a number of families who have to live with this. There are 22 other Maryland boys unaccounted for. We've tried our best to find out about all of them."

Elsewhere around the nation, the Associated Press reported that relief, a last hope dashed and shock were the reactions of some of the families and relatives of the 12 American pilots whose bodies were handed over by the Vietnamese. The AP gave this account:

"It's just such a shock right now. I don't think I can say anything about it," said Jean Eaton of Narragansett, R.I., after hearing about the recovery of her husband's body.

Maj. Curtis A. Eaton, an Air Force pilot, bailed out of his burning F-105 fighter over Vietnam on Aug. 14, 1966. He used an emergency radio to signal for help, and was listed as missing in action.

Eaton was declared dead last September after his name appeared on a list released by Vietnam of Americans killed in action.

"It's over for me," said Virginia Capling, widow of Air Force Lt. Col. Elwyn R. Capling of Detroit. "After nine years of waiting. Complete silence (from Vietnamese authorities) for nine years until last September and then nothing until now."

The news that finally convinced her that her husband was no longer alive "came as a relief that he was not suffering," she said. "But it's not really a relief to wait nine years to find out your husband is dead.

In Omaha, Neb., Mrs. Frank F. Roark, mother of William M. Roark, a Navy Pilot, said she had a "mingled reaction" to the news that the remains of her son were turned over to the commission.

Roark was 26 when he was shot down while flying a bombing mission over North Vietnam April 7, 1965.

"I'm just thankful we'll have him home," his mother said. "But I'm amazed that so much time has elapsed. It takes years to really believe he's gone. You keep hoping he will walk in the door some day. It took us almost five years to come to the conclusion that he would never return."

"I'm thankful that our country made an extended effort to accomplish this," Mrs. Roark said. "A person almost has to lose a son to understand."

Roark's widow, Karen, remarried about three years ago and is now living near Montreal, Canada, with their three children, Lisa, 15; John, 14, and William, 11. The youngest child was born a week after his father was killed.

"At least it's positive proof that he died," said Cecelia Kolstad of Virginia, Minn., the mother of Navy Cmdr. Thomas C. Kolstad who was shot down in 1967.

Kolstad's wife, Ginger, has since remarried. She now lives in Garland, Tex., with their 11-year-old boy, Aron, who was 9 months oldat the time of his father's death.