Passenger traffic at Bulgaria's three main international airports fell by 9% to just over six million passengers in 2009.
Growth at the airports trebled from 2.2 million in 2000 to over 6.6 million in 2008.
During the first two months of 2010, Sofia Airport's traffic remained at the same level as 2009.
In July 2009, Burgas International Airport handled 50% more passengers compared with Sofia's peak month of August.
Varna was the busiest of the remaining two Bulgarian airports until 2003.
While Sofia's traffic is strong throughout the year, traffic at Burgas and Varna is more seasonal, according to anna.aero.