The Reagan administration "toppled" the Haitian government of Jean-Claude Duvalier in midair en route to Houston yesterday but, by the time Air Force One landed, officials realized that they had announced a coup that hadn't happened.

By the end of the day, embarrassed officials in various departments of the government were blaming each other for the erroneous announcement, which touched off celebrations by thousands of Haitian residents in Miami, New York and Washington.

"Obviously, we got bum information from people who ought to know what's going on," White House spokesman Larry Speakes said.

No one seemed to agree who these people were. The White House and National Security Council blamed the State Department, which in turn suggested that Speakes had made too definitive an announcement. There were conflicting reports about what the original "coup" report from the U.S. Embassy in Haiti had said.

Speakes' announcement aboard Air Force One, at 9:10 a.m., first sent the report around the world.

Talking to five reporters in the rear section of the presidential aircraft, Speakes said: "The White House was informed shortly before 7:30 a.m. that the government of Haiti had collapsed and the leadership, including Duvalier, had fled the country."

This information was immediately filed from Air Force One on a conference call by United Press International and The Associated Press.

Nearly two hours later, UPI phoned veteran White House correspondent Helen Thomas aboard the plane to cite "conflicting reports" about whether the coup had taken place. She sent an urgent message to the front of the plane for Speakes, who came back and said the situation "is not as clear as we first thought it was."

Reporters then stopped national security affairs adviser John M. Poindexter, en route to the washroom in the rear of the plane, and asked what information he had received. "The situation is too uncertain for us to be positive about," Poindexter said. Later, he said the situation was "confusing."

Just before the plane landed in Houston for the space shuttle memorial service, Speakes told reporters that the administration was unsure about earlier U.S. Embassy reports that Duvalier had fled.

In Washington, officials agreed only that others were to blame.

At the White House and National Security Council, fingers were pointed at the U.S. deputy chief of mission in Haiti, Stephen P. Dawkins. Officials said he was responsible for the original report to the State Department that Duvalier had fled and been replaced by a government that was half-military and half-civilian.

But in Port-au-Prince, U.S. Embassy spokesman Jeffrey Lite said widespread rumors in Haiti that Duvalier had left the country were reported to Washington as rumors.

At the State Department operations center, which received the report, there was confusion, with officials saying it was uncertain whether the embassy had made clear that the reports were only rumors.

There was further confusion about what the operations center had told the White House. State Department spokesman Bernard Kalb, at his noon briefing, told reporters "there were a variety of conflicting reports and some reports may have tilted in that direction of a coup ." But NSC officials who received the State Department calls insisted they were told flatly that a coup had taken place.

This report was received at 7:23 a.m., White House officials said. At 7:50 a.m., the report was incorporated into a report by Poindexter. At 8 a.m., White House chief of staff Donald T. Regan briefed senior staff officials, including Speakes, on the coup. At 8:40 a.m., as the president was en route to his helicopter for the flight to Andrews Air Force Base, he was told that a coup had taken place.

"Somewhere in the transmission line, something had been dropped out," said Speakes, who later in the day said that further reports gave no evidence of a coup attempt.

But the early reports and other rumors swept through the anti-Duvalier Haitian communities. The rumors included false reports that hundreds of Duvalier backers had applied for U.S. and French visas.

U.S. officials said they have hesitated to give even quiet backing to moves to oust Duvalier because the lack of strong unions, parties or other institutions made it very uncertain who might succeed him.

The International Monetary Fund, with tacit U.S. approval, told Haiti in September that a $12 million loan would not be forthcoming because Haiti was not observing the terms of an earlier pact.

Private bankers took that as a signal that the government was bankrupt, and a wave of foreclosures followed.