MANILA, SEPT. 30 -- A continuing climate of political uncertainty is creating a widespread mood of antigovernment pessimism and raising serious new questions about the ability of President Corazon Aquino to survive in office, according to political analysts, opposition leaders and foreign diplomats.

The uncertainty appears fueled by fears of another coup attempt, bolder communist guerrilla attacks and the government's seeming inability to articulate a national agenda for solving the country's economic ills, these sources said.

Concern over another coup attempt by forces loyal to August coup leader Col. Gregorio (Gringo) Honasan, who is still at large, put the weary military on full alert again today amid reports of unusual troop movements north of Manila. Hundreds of residents awoke this morning to the sound of F16 fighter jets swooping over the city, unaware that the flight was part of a long planned aerial demonstration by the U.S. Air Force.

The government appeared preoccupied today, responding to a secret report that allegedly listed the names of more than 100 communist sympathizers in the Philippine Congress and the top ranks of the administration. The military was trying to determine how another right-wing renegade colonel, Reynaldo Cabautan, who took part in a failed coup attempt in January and is also at large, managed to hold a televised press conference last night in a downtown office building.

The day's events only added to the appearance of confusion and instability even as Aquino prepared to bolster her image with a series of public trips around the country.

Almost 20 months after Aquino took power in a popularly backed military revolt, diplomats, journalists and political analysts have begun to question seriously how long she will remain in office. "It's out of her hands," said one well-informed diplomat. "Her survival depends on what others do in the next few weeks." He said the "others" included the military as well as Honasan and his men.

Aquino's sagging political fortunes have caused a rift among foreign diplomats here. Political officers tend to paint a more optimistic picture of her prospects; military attaches, who seem overwhelmingly gloomy, see the government as too distracted to combat the insurgency successfully.

Among the Philippines' neighbors in the Association of Southeast Asian Nations, or ASEAN, several governments are known to prefer transferring the December summit meeting, scheduled to be held in Manila, to another venue.

The "People Power" coalition that united last year to depose the government of Ferdinand Marcos -- leftists, the business community, the middle class and the Catholic church -- appears to have split. A pro-Aquino rally two weeks ago brought out fewer than 3,000 people.

"The People Power organizational structure is gone, and her image has faded among its leaders," said one western diplomat.

Members of the legal left, including students and labor unions, have deserted the government in the face of what they charge is Aquino's shift to the right. Many of the marchers who mourned slain leftist leader Leandro Alejandro at his funeral yesterday carried placards directly critical of "The U.S.-Aquino dictatorship."

Military leaders, who were instrumental in forcing Marcos from power, appear to have grown increasingly estranged from the Aquino government because of what they perceive to be her antimilitary bias and weakness in fighting the communist insurgency. Surveys of military camps and the analyses of foreign defense attaches suggest that the majority of armed forces personnel support the grievances articulated by Honasan. "There is a lot of sympathy for Honasan," said one pro-Aquino governor. "He took action."

Spokesmen for the conservative business community have become some of Aquino's harshest critics. They say her failure to articulate a coherent long-term national agenda is stifling investment opportunities. "The business community likes stability," said one pro-Aquino businessman. "There is no feeling of stability now."

The powerful Catholic church also has become more critical. Cardinal Jaime Sin, the influential archbishop of Manila, has chided the government publicly for failing to curb official graft and corruption and live up to the ideals of the Feburary 1986 revolution.

Even though Vice President Salvador Laurel's break from Aquino's government earlier this month was considered a politically opportunistic move by analysts here, his resignation as foreign minister seemed to illustrate the unraveling of the coalition of her supporters.

In interviews with business executives, diplomats and progovernment and opposition politicians, almost no one is willing to bet that Aquino can last through the next 4 1/2 years -- the remainder of her term -- and turn over power to a legally elected successor in 1992. At the same time, these sources can point to no alternatives to Aquino remaining in power.

Few here see Aquino voluntarily relinquishing the presidency, given her own sense that she has some kind of divine mission to save the country following the 1983 assassination of her husband, Benigno Aquino. Rather, they say, if Aquino leaves office, or relinquishes power to some kind of a ruling council, it would be a move forced upon her, perhaps by the military.

Laurel's break, while largely played down by local analysts, seems to pose the gravest threat to Aquino's tenure, in the view of many foreign diplomatic observers. Despite his public denials, Laurel appears poised to join forces with Aquino's opposition, particularly the ousted defense minister, Sen. Juan Ponce Enrile. Such a move would give Aquino's right-wing opponents an ally who can legally and constitutionally succeed her should she relinquish power before the end of her term.

"His defection is a new danger," said one western diplomat. "It effectively puts the vice presidency in opposition hands. He himself is an opportunist, but an alliance with Enrile might embolden anyone who had thoughts of removing her."

The succession issue is crucial since any military coup here would mean a certain cut-off of American and other foreign aid. Opposition politicians interviewed, however, said that a Laurel takeover might be considered more palatable to foreign governments.

Laurel, in an interview last week, said he may seek to revive the conservative Nacionalista Party, to which he and Enrile used to belong. He said he sees a center-right grouping that would likely include himself and Enrile, whom he described as "in the center."

Aquino, meanwhile, has scheduled several trips around the provinces to hold talks with the military. She has also agreed to hold an open question-and-answer session with foreign correspondents in late October, marking a break from her previous policy.

Recent visitors to the palace have reported that her mood is relaxed, even cheery.

"Filipinos are masters of the art of brinksmanship," said one Asian diplomat. "They take things to the brink of crisis and then pull back. Maybe they'll do it this time."