Fils-Aime was appointed by the Caribbean island nation's transitional council over the weekend to succeed Garry Conille, who only lasted in the role six months.
The council and the new prime minister are tasked with preparing for long-delayed elections amid a deep political and social crisis marked by growing hunger and frequent episodes of raging gangland violence.
"Obviously, the first unavoidable challenge is the reinstatement of security," Fils-Aime said in a crowded room at the prime minister's official office, known as Villa d'Accueil, attended by diplomats and other dignitaries.
"Security of the people, security of the goods and infrastructures. Food security and freedom of movement across the entire national territory," he stressed, in a nod to areas controlled by powerful gangs.
Fils-Aime is the son of well-known Haitian activist Alix Fils-Aime, who was jailed under the regime of former dictator Jean-Claude "Baby Doc" Duvalier, who ruled from 1971 until he was overthrown by a popular uprising in 1986.
Earlier on Monday, a Spirit Airlines flight to the capital Port-au-Prince was struck by gunfire, injuring a flight attendant who was grazed by a bullet, according to a Miami Herald report, and forcing the plane to divert to the neighboring Dominican Republic.
The incident marks the latest eruption of violence blamed on the gangs that control most of the capital, as well as key roadways and other infrastructure. The gangs, whom Fils-Aime dubbed "bandits" in his speech, have often targeted the Toussaint Louverture International Airport.
In a statement, Spirit confirmed the plane was damaged but that no passengers were injured.
A video circulating on social media showed where a bullet pierced the rear exit door as well as striking an overhead bin across the aisle. Reuters was unable to immediately verify the authenticity of the video.
All flights in and out of the airport have been halted, according to a travel advisory from the U.S. embassy in Haiti.
The embassy "is aware of gang-led efforts to block travel to and from Port-au-Prince which may include armed violence, and disruptions to roads, ports and airports," it added.
Armed gangs in Haiti's capital have shot at aircraft in recent weeks as the security situation has worsened. Last month, a U.N. helicopter was hit by gunfire over Port-au-Prince.
