Events leading up to the presentation of findings yesterday and today in Manila include:

Aug. 21, 1983 -- Philippine opposition leader Benigno S. Aquino Jr., 50, returning home after three years of self-imposed exile in the United States, is shot once in the head seconds after leaving a China Airlines plane in the custody of military guards at the Manila International Airport.

Aug. 22 -- President Ferdinand Marcos says Aquino's assassin was a "professional killer" but said the man has not been identified yet.

Aug. 24 -- Marcos appoints five judges to a fact-finding commission to investigate the killing.

Aug. 30 -- Philippine military identifies Aquino's killer as Rolando Galman, 33, a hired gun who the military says had ties to organized crime and Communist insurgents. Maj. Gen. Prospero Olivas, the chief of police in Manila who is heading the military investigation, says Galman was "a notorious killer" and "a gun for hire."

Sept. 4 -- Galman's girlfriend, Anna Oliva, 29, and her sister, Catherine, 22, are taken from a nightclub where they worked by two armed men whose car was equipped with a telephone and a walkie-talkie. They are still missing. Galman was reported to have spent the three nights before the assassination with Anna Oliva in a motel near the Manila airport, where he was guarded by unidentified men.

Sept. 21 -- At least 10 people killed and 143 injured in the worst street violence since martial law was imposed in 1972.

Oct. 3 -- President Reagan cancels plans to visit the Philippines, Indonesia and Thailand in November because of U.S. concern about political instability of the Marcos government.

Oct. 10 -- All five members of fact-finding commission resign after the second designated chairman refuses to accept post. First chairman, Chief Justice Enrique Fernando, is forced to resign after lawsuits challenged the commission's legality and impartiality.

Oct. 17 -- The Philippine government asks for a 90-day moratorium on the repayment of its $25 billion foreign debt after street protests and loss of financial confidence produced a massive flight of capital.

Oct. 22 -- Marcos names five private citizens to new fact-finding board. Board is headed by Corazon Agrava, a retired justice of the Court of Appeals. The board's inquiry lasted 10 months. As evidence, the board gathers 1,430 photographs, more than 1,400 documents and exhibits, 22 video and audio tape recordings and more than 20,000 pages of transcribed testimony from witnesses. The board questioned 193 witnesses, including Marcos' wife Imelda and Gen. Fabian Ver, 64, a trusted confidant of Marcos and chief of staff of the armed forces since 1981. Ver has all the vital units of the military under his direct command. His three sons are all in the Army and one is the head of Marcos' palace security.

Testifying on her 55th birthday in July, Imelda Marcos denies having said: "If Aquino comes home, he's dead."

The board holds hearings in Tokyo and Los Angeles as well as Manila.

July 6, 1984 -- Board ends its public hearings and begins evaluating the evidence given in open and closed sessions.

Sept. 19 -- A senior official of the board says the board has determined that the Philippine military plotted to kill Aquino and Galman but that there is no evidence that either Marcos or his wife Imelda were involved. These findings come after opposition leaders and independent lawyers' groups charge that Aquino was the victim of a military plot.

Sept. 20 -- Marcos says the report of the board will be referred to "the proper authorities for prosecution," whatever it concludes.

Oct. 12 -- Additional details about the alleged military conspiracy emerge as the legal panel of the board implicates 18 military personnel and one civilian in a 479-page report.

The report says Aquino was shot by one of two military escorts. Heading the list of "participants" is Ver, who is cited for having ordered a plan to secure Aquino's arrival but which ended in his death. Also named in the report is Brig. Gen. Luther Custodio, 49, the commander of the elite Aviation Security Command in charge of security for the airport.

Oct. 17 -- Board denounces the sudden retraction of secret testimony by a key civilian witness as "a desperate attempt by some quarters to discredit the board and its findings."

Oct. 23 -- Board chairman presents Marcos with her report implicating seven military men in a conspiracy to kill Aquino.