* Sees passengers doubling to 7 billion by 2034

* Previous forecast was for 7.4 billion

* China growth slows; Brazil, Russia struggle

(Adds more details on forecasts)

FRANKFURT, Nov 26 (Reuters) - Slowing growth in China, the fastest growing market for air travel, will dampen global demand for air transport, the International Air Transport Association (IATA) said as it cut its long-term forecast for global passenger numbers.

Concerns over the outlook for global economic growth have been looming large in recent months, prompting the heads of the world's 20 largest economies to warn this month that growth around the world was uneven and falling short of expectations.

A spate of terror attacks have also cast a pall over international travel, with security worries driving down airline and hotel stocks earlier this week.

"Economic and political events over the last year have impacted some of the fundamentals for growth," IATA's head Tony Tyler said in a statement on Thursday.

IATA now expects the number of air passengers to reach 7 billion by 2034, doubling from the 3.5 billion expected for 2015, with a 3.8 percent average annual growth rate.

The association, whose around 260 members account for 83 percent of global air traffic, previously saw passenger numbers rising by an average of 4.1 percent per year to 7.4 billion in 2034.

IATA pointed to slower economic growth expectations for China as the main reason for its downgrade, but said it was still the fastest growing market in terms of extra passengers and was set to overtake the United States as the world's largest passenger market by 2029. China will account for around 1.19 billion passengers by 2034.

Brazil and Russia meanwhile are struggling, IATA said, partly due to falling oil and commodity prices, while Russia is also feeling the effect of economic sanctions.

IATA is due to give an update on its outlook for airline profits in 2015 and 2016 on Dec 10. It currently forecasts global airline profits of $29.3 billion in 2015, almost double that of last year.

(Reporting by Maria Sheahan and Victoria Bryan; Editing by Georgina Prodhan and Elaine Hardcastle) ((maria.sheahan@thomsonreuters.com; +49 69 7565 1286; Reuters Messaging: maria.sheahan.thomsonreuters.com@reuters.net))