A Libyan Arab Airlines aircraft was refused permission to land at Malta Airport on Wednesday and turned back to Libya, airport sources said.
But the daughter of Libyan leader Muammar Gaddafi denied an Al Jazeera report that she had been on board the aircraft.
"I was surprised when friends abroad told me about this report," she told Libyan state television outside a family residence that was damaged in a 1986 US bombing raid that targeted her father.
"I am steadfastly here," she said.
She denounced channels that carried the report as "mercenary and treasonous".
She said she could not confirm reports that the United Nations had dropped her as a goodwill ambassador. "But Libyans who know me... know well that I am a goodwill ambassador regardless of whether it is at the United Nations or not."
The aircraft, an ATR42 turbo-prop, flew to Malta without prior notice and when asked whether it had permission to land, the pilot gave details of a flight which was supposed to have landed in Malta on Tuesday, the airport sources said.
Landing permission was refused and, after circling for 20 minutes while trying to reverse the decision, the pilot decided to return to Libya.
Gaddafi's four-decade rule of oil-rich Libya has been shaken by violent protests which reached the capital Tripoli on Monday. Eastern Libya has been out of Gaddafi's control for several days, according to local people.
Maltese soldiers were seen entering the airport as the aircraft approached.
Troops were still guarding two Libyan Air Force Mirage F1 fighters whose pilots defected to Malta on Monday, saying they had been ordered to bomb anti-government protesters in Libya's second city Benghazi.
The pilots, both colonels, remained in custody. One of them has requested political asylum.