The International Air Transport Association (IATA), which represents most global carriers, also warned of a looming trade war if Europe moves ahead with plans to force airlines to join an emissions trading scheme next year. China said it would support legal action.
Airlines say the scheme, designed to tackle growing emissions from the aviation industry, will only increase costs and add to pressures already caused by the sluggish global economy.
"The efficiency gains of the last decade and the strengthening global economic environment are balancing the high price of fuel," the IATA's director general, Giovanni Bisignani, told the group's annual general meeting in Singapore.
"But with a dismal 0.7 percent margin, there is little buffer left against further shocks," he said.
The IATA $4 billion profit forecast compares with an $8.6 billion forecast on March 2, just before the Japan earthquake and tsunami triggered a nuclear meltdown at a power station. Since then, the Arab uprisings have spread and oil prices have traded well above $100 a barrel.
The forecast would also mark a drop of more than three-quarters from the industry's estimated 2010 profit, which was raised to $18 billion from $16 billion.
Economists say the industry's outlook is a guide to the strength of cyclical recovery in developed markets and growth in emerging economies, which rely heavily on air transport.
Airlines rebounded faster than expected from recession last year, helped by higher traffic and a drive to keep a lid on spare capacity. But far too rapid expansion in capacity, a series of external shocks and higher oil prices have hit the industry hard this year.
Airlines had been bracing for lower 2011 forecasts at this week's major conference as fears grow over the global economy.
IATA is forecasting a $110 per barrel average oil price in 2011, up 15 percent from $96 last year, adding to the case for airlines to raise airfares or fuel surcharges to cover the rising cost of doing business.
Qantas Airways was "looking at more increases going forward," its chief executive, Alan Joyce, told Reuters. "Hedging just gives you time."
IATA warned that capacity was set to expand 5.8 percent in 2011, outstripping a 4.7 percent increase in demand. The 1.1 percentage point gap is sharply higher than the 0.3 percent previously forecast.
Bisignani has said a lack of discipline could dent the industry's recovery as airlines jostle for market share.
Other Costs
In a move with major cost implications for the industry, Rolls-Royce is set to build a new engine to beef up the A350 jetliner being developed by Airbus, industry sources said.
Until now, Airbus and Rolls had defended the engine as an all-rounder capable of powering three separate models of the mid-sized A350, which is designed to carry 270 to 350 people.
In Europe, the EU's planned Emissions Trading Scheme (ETS) would force carriers to buy permits for each tonne of carbon dioxide they emit above a certain cap.
The plan is meant to tackle growing emissions from the $500 billion aviation industry, which is responsible for about 2 percent of mankind's greenhouse gas pollution.
Governments and airlines have been piling on pressure, some describing the forced inclusion of global airlines as illegal.
The EU has offered to exempt airlines of countries that can prove they are taking equivalent steps to cut emissions.
Representatives from developing countries slammed the proposed rules and said they were unfair.
"Indian airlines which fly overseas, such as Kingfisher, have already made their views known to the minister of civil aviation," said Vijay Mallya, chairman of Kingfisher Airlines, which has the second-largest market share of India's aviation industry.
"We do not have the same level of sophistication or maturity in trading of
