In the months before this week’s fatal crash of a Spanair jet in Madrid the airline’s workers warned management repeatedly that passengers’ safety was being put at risk by the “chaotic” way the airline was being run.

The Spanish pilots’ union, Sepla, said in a series of e-mails to the airline’s management that the airline’s day-to-day operations were a disaster. It also cautioned that its fleet of older MD80 series aircraft, of the type that crashed on Wednesday, killing 153, was not being updated quickly enough.

In an April 2007 e-mail to Lars Nygaard, the chief executive of Spanair at the time, a union representative wrote: “The lack of resources and their quality on the ground, the repeated AOGs [grounded aircraft] in the fleet, the scarcity of crews and the system of movement of crew members mean that the general feeling is one of operational chaos that places the passengers at risk.”

The next month the union again wrote to the management, saying: “The operation continues to be a disaster and is getting worse by the day.”

The e-mails were published yesterday by the Spanish newspaper El Mundo. It was not known immediately how the company responded to the warnings.

Spanair has rebuffed criticism of the company. It insisted that passenger safety was never compromised by its financial woes and said that the airline had enjoyed a good safety record in its 22 years of operation.

Scandinavian Airlines System (SAS) has been trying to sell loss-making Spanair for the past year.

It failed to find a buyer and had drawn up plans to axe a quarter of the 4,000 staff and cut the number of services.

Aviation analysts said that it would be very difficult for Spanair to survive this crash as passengers may be unwilling to trust it again. One said: “This is the final nail in Spanair’s coffin and may take down SAS as well. It is very hard to survive the reputational damage from a crash like this and most airlines don’t.”

The company’s management deflected questions on its future this week. “We are firmly focused on supporting the families,” Marcus Hedblom, Spanair’s general manager, said. “The question [of viability] is not really up for discussion at the moment.”

The latest e-mails show that workers feared that the continual cutbacks were affecting its ability to offer passengers a proper service and maintain safety standards. “We want to avoid the passenger coming into conflict with us over something we are not responsible for,” a union representative wrote in June 2007. The passenger “should come and go in ‘an atmosphere of cordiality, comfort and safety’ ”.

The union’s warnings about the number of “AOGs” — Aircraft on Ground — also point to concerns about the state of Spanair’s fleet of aircraft. It said that the older McDonnell Douglas jets of the type that crashed this week were not being replaced fast enough.

“The MD fleet has not been renewed in favour of A320s in the agreed timeframe,” the union wrote in January 2008.

The airline, which is based in Majorca, has 36 MD80 series aircraft. Spanair executives said that they saw no reason to ground the fleet until a cause of the crash could be determined.

The theory that the aircraft suffered a catastrophic failure of one of its engines has lost ground as new evidence has come to light. Video footage that has been found of the crash did not, as some witnesses claimed, show the left engine on fire before it hit the ground, Spanish media reported.

Many aviation experts had already cast doubt on the hypothesis, pointing out that the aircraft are designed to be able to take off even if one of its two engines fails.

Furthermore, a failure of the left engine should make the jet veer in that direction. In fact, the jet rose around 50 metres into the air before crashing to the right of the runway.

“There was more than one failure,” the head of Spain’s Civil Aviation authority, Manuel Bautista, told El País newspaper. “One engine does not cause an accident.”

Aviation experts also doubted that a problem that led the aircraft’s pilot to abort his first take-off attempt could have been responsible for the accident.

Spanair said that the pilot had noticed that an air intake under the cockpit window was overheating on his first approach to the runway. Maintenance staff disconnected the power to the intake and cleared the jet for its second, ill-fated, take-off.

Times Recommends

• Tehran cannot live up to its rhetoric
• The new unicycle that will ‘change the world’
• We cannot wish away Iran’s bomb