BRUSSELS (AP) -- The Airbus 310 that crashed Tuesday was 19 years old, yet experts say older planes can keep going strong for years as long as companies are willing to invest what it takes to keep them sky-worthy.

"Aircraft are usually retired due to economics rather than due to wearing out," said Bill Voss, president of the Flight Safety Foundation in Alexandria, Virginia, an international aviation safety think tank.

Still, whenever an accident involves an older passenger aircraft, the age of the plane often becomes a focus of speculation about the cause of the crash.

After the crash Tuesday of a Yemenia jet with 153 people on board near the Comoros islands, some French Comorans questioned the airline's maintenance and safety records. Others said they had been complaining about the airline for years, but authorities brushed off their comments.

But analysts note that most of today's airliners can be kept flying almost indefinitely if regular inspections prescribed by the manufacturer are carried out. Although some airlines highlight in their advertising the newer aircraft in their fleets, newer and older planes tend to have similar safety records.

"This is an older aircraft. But older aircraft can operate safely for decades if provided with proper maintenance," said Capt. Harry Eggerschwiler, chief of operations for the African Civil Aviation Authority.

The Airbus A310, the second model designed and manufactured by the European consortium, made its debut in the late 1970s. Deliveries ended 20 years later, when Airbus replaced it with the newer A330 and A320.

During two decades in production, the A310 had a comparable safety record to other jetliners. It earned a reputation among pilots as a relatively forgiving plane, easy to fly and responsive to commands.

Planes with service histories such as the A310 that crashed -- with 52,000 flying hours and some 17,000 landing and takeoff cycles -- remain common in the inventories of U.S. and European airlines.

Yemenia airways itself has a solid safety record. In 2008 it passed the International Airline Transport Association's operational safety audit, a rigorous set of inspections considered an indication of high quality for any airline.

On Tuesday, the European Union's Transport Commissioner Antonio Tajani said in Brussels that the airline had previously met EU safety checks and was not on the their blacklist of unsafe airlines -- a blacklist that has over 190 airlines.

He added, however, that a full investigation was being launched amid questions about why the passengers -- who originated in Paris -- were transferred on another jet in the Yemeni capital of San'a.

"The maintenance record of the plane the Yemeni airline will definitely be examined closely," Voss said.

Yemenia has, however, long been a target of criticism for the poor condition of its passenger cabins. Recent passengers have complained about missing or faulty seat belts. In the 1960s, when it was favored by hippies flying to eastern Africa, passengers told stories of cabin attendants frying eggs on open fires in the aisles.

Stephane Salord, the Comoros' honorary consul in Marseilles, on Tuesday called the company's aircraft "flying cattle trucks." Former passenger Mohamed Ali, a Comoran who went to Yemenia's headquarters in Paris to try to get more information on the crash, said sometimes passengers stand all the way from Yemen to the Comoros on the flights.

Still, analysts have cautioned against equating the condition of the passenger cabin on any airline with the aircraft's maintenance records.

One problem that does crop up with older aircraft, particularly when a certain model has been discontinued, is the issue of fake replacement parts.

Airline companies sometimes unwittingly purchase fake parts, which are then put into aircraft by their maintenance crews. Despite rigorous international efforts to root out fake spares in the past decade, they are still believed to be in circulation.

"Pirate spare parts remain a big maintenance problem in aviation," Eggerschwiler said. "This is true everywhere in the world and not just in (developing) countries."