The global airline industry is facing a recession far more severe than the slowdown endured after the terrorist attacks of 2001, a leading aviation expert claims.

William Swelbar, a consultant to the Massachusetts Institute of Technology, told The Times that the true health of the aviation market - especially in the United States - will not become clear until this autumn, after the key holiday season.

“Many flights ... over the next few months were booked months ago, so it distorts the true picture of what is happening. What is for sure is that we are headed towards a severe slowdown. We may already be in a recession,” Mr Swelbar said.

His comments came as SilverJet, the business-only airline, left passengers stranded after admitting that it had run out of cash and had suspended operations.

Experts and aviation executives have said that record oil prices have fractured the traditional business model of most airlines.

Steve Lott, a spokesman for the International Air Transport Association (IATA), yesterday described a “perfect storm” that is heading for world airlines, to which the American market is especially sensitive.

“The economic slowdown in the US, the oil price and the weakness of the dollar are all conspiring to hit the aviation market. Americans are going to be thinking hard about whether they can afford to travel. It's not just economy travel. In March, globally, we saw the fastest decline in premium traffic for five years. The outlook is grim.”

Mr Lott said that airlines were being squeezed on two fronts: falling passenger traffic and rising costs, driven by the oil price.

According to IATA, global passenger traffic slowed to a 4 per cent growth rate in the first three months of this year, compared with 6.7 per cent for the same period a year earlier. Many expect traffic to shrink much further by the end of the year.

One airline executive said: “The problem is that we have already cut the fat - we did so after 9/11. There really are no more jobs to cut. The way forward is to cut capacity, big time. You are going to see planes grounded just to stem the losses and fares are just going to have to go up.”

British Airways, having bolstered its balance sheet after the 9/11 attacks with a £5.9 billion rights issue, is in better health than many rivals, but is believed to be considering ways of grounding about a fifth of its fleet.

Frances Farrow, chief executive of Virgin USA, said that if airlines fail to raise prices to respond to the increasing oil price, “everybody is in trouble by the end of the year. Everybody. Something has to happen.”

She said that older “legacy” airlines such as American Airlines and United Airlines run older and less fuel-efficient aircraft, so face an immediate disadvantage. However, United and US Airways confirmed yesterday that a merger of the two carriers would not happen “at this time”.

Many airlines have tried to avoid raising fares bacause the slowdown in passenger traffic has made competition more fierce. Instead, some have imposed fuel surcharges and extras.

Jet Blue has recently started to charge between $20 and $30 (£10 to £15) for a window seat, while American Airlines this month introduced a fee for checked-in luggage.

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