PONTOISE, France—The manslaughter trial of Continental Airlines Inc. and five aviation officials whom prosecutors blame for the fatal 2000 crash of an Air France S.A. Concorde presents “ominous” possibilities for aviation insurers and policyholders, experts say.

The criminal trial in Pontoise, France, began last week with prosecutors describing manslaughter charges against the Houston-based airline, two of its mechanics, two workers at the Concorde manufacturer and one official from the French civil aviation authority.

If convicted of manslaughter, Continental could be fined as much as $521,000 and the individuals could receive up to five years in prison and a $104,000 fine.

The Concorde crashed July 25, 2000, shortly after takeoff from Charles de Gaulle International Airport near Paris. All 109 passengers and crew aboard the Air France flight to New York were killed, in addition to four people in a hotel that the plane hit when it went down.

French safety experts determined the crash was caused by a titanium strip on the runway that had fallen off a Continental Airlines DC-10 minutes before the Air France flight took off. That titanium strip punctured the Concorde's tire, creating debris that damaged the plane's fuel tanks and caused an explosion, the safety inquiry found.

Continental mechanics used the titanium strip to replace an aluminum strip, which was unauthorized by Federal Aviation Administration regulations, according to the French investigation.

Continental, however, disputed French investigators' conclusion.

An attorney for Continental argued in court last week that the titanium strip did not cause the crash and that Air France's maintenance crew was to blame for various problems with the jet that caused the accident. Witnesses saw the Concorde on fire before it reached the titanium strip, he said.

The trial may last four months, legal experts said. The families of most victims agreed to settlements long ago in the first fatal crash involving the Concorde, which was removed from service in 2003.

Kenneth P. Quinn, a Washington-based partner at Pillsbury Winthrop Shaw Pittman L.L.P., said criminal charges are becoming “increasingly the norm for some of the more spectacular (aviation) tragedies.”

“It's certainly an ominous development for global aviation and insurers to face the prospects of criminal liability even after they've long settled the civil cases,” Mr. Quinn said. “The costs of a 10-year investigation and four-month trial can be staggering.”

Prosecutors typically have to prove that aviation officials took an unreasonably high risk that led to a crash to prove charges in such a case, Mr. Quinn said. He said there have been about 15 criminal prosecutions after air crashes during the past decade, including officials connected to the 2005 Helios Airways crash in Greece, the 2002 midair collision involving Bashkirian Airlines on the German-Swiss border and the 1996 ValueJet crash in the Florida Everglades.

Mr. Quinn said even when defendants are acquitted in such cases, criminal charges can increase the amount of damages airlines must pay and raise the possibility of punitive damages. That has influenced aviation insurers to fund the criminal defense of airlines and employees, which is excluded from typical liability policies, more than they did a decade ago.

“Increasingly, I think insurers are taking a long-term and sophisticated view that recognizes that the bar appears to be getting lower to bring these cases,” Mr. Quinn said. “The risks are getting higher that a conviction will exacerbate their exposure to higher settlement or the prospect of punitive damages.”

He and others say criminal charges can hurt flight safety by discouraging aviation officials from cooperating with investigators.

Sean Gates, a senior partner and aerospace attorney with London-based Gates and Partners Solicitors, said he advises clients to be “very guarded” during accident investigations.

“This is not conducive to the best investigation outcome, but the record of many courts of improperly using official accident reports and statements taken from witnesses without benefit of counsel compels those involved to take a defensive posture,” Mr. Gates said in an e-mail.