The aircraft was seen hoisting the flag of revolutionary forces and circling above Ajdabiya on Saturday.
Sources say several huge explosions have rocked the town and its surroundings.
This comes as fighting between opposition fighters and Muammar Gaddafi’s loyalists continue in strategically important towns.
Several pilots have defected from the regime’s air force and joined the opposition ranks over the past weeks.
Sources say opposition forces are attempting to form a self-sufficient military due to mistrust between revolutionaries and Western forces.
NATO is increasingly coming under fire from the opposition in Libya over its lack of response to the killing of civilians by regime forces.
A source in the revolutionaries’ camp in Benghazi criticized NATO for turning a blind eye to civilian deaths in Misratah.
Forces loyal to Gaddafi have been pounding Misratah over the past weeks, resulting in heavy civilian casualties.
The Western allied forces which conduct air raids on Libya to enforce a UN no-fly zone have not intervened in Misratah so far.
Moreover, the revolutionary forces slammed NATO after its warplanes hit the fighters’ tanks near Brega, killing several people and wounding over a dozen. The alliance admitted to the killings but refused to offer a formal apology.
The head of the opposition’s armed forces Gen. Abdul Fattah Younis says NATO’s inaction has allowed government troops to advance and kill people in Misratah and other cities.
Younis has threatened to ask the United Nations Security Council to suspend the NATO mission in Libya if the military alliance does not do “its work properly.”