An AFP journalist said the Tunisair plane was prevented from moving for several hours by young people from the Sug Jomaa district of the capital who sat around it.
Around 50 cars also drove onto the airport tarmac, with some parking under the Airbus A-320 which had been due to take off for Tunis at 5:00 pm.
The plane eventually took off around 11:00 pm, witnesses told AFP, after authorities reassured those who were blocking the plane that perpetrators of violence would be brought to justice.
"We were promised that steps will be taken by Wednesday," Ahmed Dernaoui, who was one of the demonstrators, told AFP.
The protesters said that former rebel fighters from their area were called in as reinforcements this week to Bani Walid, some 170 kilometres (105 miles) southeast of Tripoli but they were attacked by elements from the former regime.
Thirteen of them were killed, according to National Transitional Council (NTC) member Abderrazak Abdessalam al-Aradi, who came to the airport to try to defuse the tense situation.
"We just want justice. If not, we will make justice ourselves," Mohammed Belhaj, another protester, told AFP.
One of his colleagues, Hosni Berbesh, added: "They're nothing but chameleons in Bani Walid. They've only changed colour, but they still support the old regime."
The Sug Jomaa residents are demanding the arrest of murderers and the disarmament of brigades in Bani Walid. The NTC is expected to discuss the incident on Sunday.
In Tunis, the airline's director of exterior relations Sulafa Mokkadem told AFP: "These were armed Libyans who wanted to get on the aircraft to verify the identities of wounded on board.
"The captain refused to let them on board. The aircraft did not take off. This action was not directed against us or Tunisia. It is a dispute between Libyans."
She said there were some 50 people on board the airliner, "mostly Libyans".