Polynesian Airlines flew over 2,000 passengers more last month between Samoa and American Samoa than in December 2008.
The Chief Executive Officer, Taua Fatu Tielu, says he believes the increase is due to the closure of competitor South Pacific Express.
SPEX suspended its service in September.
Another factor which contributed to the increase is the re-opening of Fagalii Airport in Apia.
Travelling to American Samoa from Fagalii is 15 minutes faster compared to flights from Faleolo Airport.