The International Air Transport Association says passenger demand grew 5.9 percent last year but lagged behind capacity increases.
The group, which represents some 240 major airlines, says the airlines increased their available seats by 6.3 percent meaning average loads declined slightly in 2011.
IATA said in a statement Wednesday that the cargo market contracted 0.7 percent last year.
The group said the weak euro boosted business travel, as passengers from elsewhere took advantage of cheaper fares.
It noted that travel to and from Japan was badly affected by the earthquake with demand down more than 15 percent.
IATA Chief Executive Tony Tyler says business conditions will remain tough in 2012 and called for political measures to cut bureaucracy for airlines.