At least 150 of 175 passengers onboard a Spanish airliner were killed when the plane careered off a Madrid airport runway and broke up in flames on Wednesday, officials said. The aging McDonnell Douglas MD-82 of Spanair's Flight K5022 was taking holidaymakers to the city of Las Palmas in the Canary Islands at the height of Europe's vacation season when the country's worst air crash in more than 20 years occurred at 2:45 P.M. local time. The plane was just barely airborne when it veered right, crashed and broke into pieces, officials and reports said. Development Minister Magdalena Alvarez said the cause of the accident seemed to be “an error in takeoff”. But Spanish media and a source close to the situation said the plane's left engine, made by Pratt & Whitney, had caught fire. The plane was originally due to take off at 1 P.M., but after pushing back from the terminal and approaching the runway it returned because of a mechanical problem, a source close to the situation told Reuters. The source added he did not know what the problem was or what action mechanics took. Spanair, owned by Scandinavian airline SAS, said the names of the passengers and crew would only be released after families have been notified. Spanair's managing director Marcus Hedblom described it as “the worst thing that could happen” and expressed his condolences to the families of those killed. SAS, the Scandinavian airline which owns Spanair, said a special team had been set up in Madrid. “SAS is doing everything possible to help passengers and next of kin and to assist Spanish authorities.” Spanish Prime Minister Jose Luis Rodriguez Zapatero interrupted his holidays and the Spanish Olympic Committee said the Spanish flag would fly at half mast in the Olympic village in Beijing. The MD-82 is a medium-range single-aisle plane, popular with regional airlines. It is a member of the MD-80 family of planes made by US manufacturer McDonnell Douglas, which had been bought out by Boeing Co. in 1997. American Airlines had to cancel 3,000 flights earlier this year after US authorities ordered them to ground MD-80 series planes to check their wiring. Boeing spokesman Jim Proulx said the company would send at least one person to assist in the investigation of the crash as soon as it receives an invitation from Spanish authorities. The DC-9/MD-80 family of twin-engine medium-range airliners enjoyed wide popularity among the world's airlines in the 1970s, 80s and 90s. But it has had a number of fatal accidents, the deadliest of which was a crash of Slovenia's Adria Airways flight in Corsica in 1981, when all 180 people on board perished. Spanair has had a good safety record until now. However, five passengers on a Spanair flight from Spain's Basque region to Barcelona were injured in an emergency evacuation on January 9, 2006.