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Hani Mohammed, Associated Press
Backdropped by a building decorated with posters showing Yemen's President Ali Abdullah Saleh, Yemenis walk in an alley of the old city of Sanaa, Yemen, Monday, Jan. 23, 2012.

SANAA, Yemen — The departure of leader Ali Abdullah Saleh for medical treatment is doing little to calm Yemen — the opposition movement is skeptical that he'll stay away and many are looking to presidential elections as the real test of regime change.

A wave of mutinies against the air force commander provided the latest example of how Yemenis are impatient for reform and how tenuous the security situation remains in the key U.S. ally in the fight against al-Qaida.

"The post-Saleh era has not started yet," said political activist Habib al-Ariqi. "His family, his interest groups, those who benefited from him for years and years still hold the strings of power."

Yemen's nearly year-old uprising has taken a different path from other revolts across the Arab world. After months of mass protests demanding Saleh's ouster and mounting international pressure, the president signed a deal brokered by Yemen's Gulf neighbors and backed by the U.S. to pass power to his vice president. That is the first step in a process meant to give the country a new constitution, president and elected parliament.

To persuade Saleh to sign, a clause protecting him and those associated with his government from prosecution was added. Diplomats involved in the process have said the deal wouldn't have gone through without it.

Some in Yemen suspect Saleh is still trying to slip out of the deal and stay in power, even if it's behind the scenes.

Despite the concerns, tens of thousands of protesters took to the streets in cities nationwide Monday to welcome Saleh's exit and warn the remnants of his regime against trying to hold on to power.

"Saleh left the country, he will be followed by the soldiers and the sons," protesters chanted as they marched in Taiz. In the central city of Bayda, they shouted, "we have achieved our goal." And in the southern city of Ibb, tens of thousands chanted, "to the world, we are send you Ali, the terrorism maker."

Saleh flew to Oman late Sunday in the first stop of a trip that is to eventually take him to the U.S. for medical treatment, some two months after signing the deal to pass power to his vice president, Abed Rabbo Mansour Hadi.

U.S. officials said the Yemeni leader would travel to New York this week, and probably stay in the country until no later than the end of February. U.S. officials believe Saleh's exit from Yemen could lower the risk of disruptions in the lead-up to presidential elections planned there on Feb. 21.

The leader was badly burned during a June attack on his compound in Yemen. He received medical treatment in neighboring Saudi Arabia for three months. American officials had hoped he would remain there, but the Yemeni leader returned home and violence worsened anew.

Saleh, who maintained power for more than 30 years through a mixture of political acumen, manipulation, patronage and violence, has emerged in the best position so far of the autocratic Arab leaders who have been ousted since a wave of revolutions began last year.

Tunisia's former leader, Zine El Abidine Ben Ali, fled to Saudi Arabia and has been convicted in absentia for corruption and other crimes during his regime. Egypt's Hosni Mubarak is on trial and faces a possible death penalty, and ex-Libyan leader Moammar Gadhafi was killed after being captured by rebels in October.

The outgoing Yemeni president's farewell speech on Sunday raised new concerns among protesters who have rejected the immunity clause, saying Saleh must face justice for his alleged role in a brutal crackdown that rights group say has killed some 200 protesters since it began last January.

In his speech, Saleh said he had transferred all responsibility to Hadi, but he also promised to return to Yemen before the elections as the head of his party.

Moreover, the power-sharing deal includes Saleh's party as part of national unity government with a share of ministerial portfolios. Even the ministries run by the opposition include high ranking officials who are members of Saleh's party.

Saleh also has left behind family members and staunch loyalists who belong to his tribe and who are still holding key and influential positions in the military and the government.

Saleh's son, Ahmed, commands the powerful Special Forces and Republican Guard which field the most highly trained troops to be deployed to the streets to crush protests. The other top internal security forces are under the command of the president's nephews, Tareq, Yahia and Ammar. All are better equipped than the regular military, parts of which have defected to join the protesters.

That has led to power struggles and delayed reforms within state institutions. Violence also has persisted, and al-Qaida's active Yemen branch has taken advantage of the political instability to increase its foothold.

The insecurity was underscored over the weekend by a wave of mutinies, which spread to four air bases by Monday, as lower ranking airmen demanded the ouster of the country's air force commander, Maj. Gen. Mohammed Saleh, the president's half brother.

Col. Mohammed al-Qubati at the air base in the capital Sanaa said about 200 airmen were continuing a protest they started Sunday. They were pushed from the air base by loyalist troops but moved into the city, protesting at Hadi's nearby residence. Officers said that the garrisons of two more bases, at Taiz in the south and at Hodeida in the west, were also protesting.

"No to injustice, no to dictatorship, no to corruption," read one banner hanging on Al Anad's walls.

In a sign of the difficulties in uprooting Saleh's influence, Yemen's official news agency continued to call him "His highness, the brother, the president of the republic" on Monday. The agency is run by the top media official of Saleh's General People's Congress party, Tarek al-Shami.

Key public sector companies like the main supplier of fuel, The National Oil company and tobacco company also are run by Saleh's in-laws.

"Only when we name a president will change start, and then we can talk about the post-Saleh era," al-Ariqi said.

Michael reported from Cairo.