(CNN) -- Every once in a while, air travelers call up the Flight Safety Foundation and ask: Which airline should I fly? Is this one considered statistically safer than another?
The response may be surprising.
"There is no way to answer that question," said Emily McGee, director of communications for the nonprofit international group headquartered in Alexandria, Virginia. "There's no official way that's done."
You can access government databases and look up plane accidents by airline. But you won't find any official safety grades or rankings assigned to carriers.
The National Transportation Safety Board investigates accidents, but it does not rate airlines for safety, spokesman Keith Holloway said. Neither does the Federal Aviation Administration.
"The rationale behind that is that, in this country at least, airline accidents are such rare occurrences that there is really no meaningful statistical measure of safety that you could assign to any one airline," FAA spokesman Les Dorr said.
The European Aviation Safety Agency also does not offer airline safety ratings, according to Safety Information and Communications Officer Dominique Fouda.
The European Commission -- the executive body of the European Union -- does maintain a list of airlines "found to be unsafe," which are banned from operating in European airspace.
But there is no central repository for collecting data from all the airlines around the world that would help determine their statistical safety or risk, said Greg Feith, an international aviation safety and security consultant and a former senior NTSB investigator.
"Foreign authorities require different reporting of events, accidents and incidents. There is no world standard; that's the problem," Feith said.
Hunting for clues online
In the absence of curated data, non-professionals are trying to address questions like: How do passengers determine which airlines are statistically safest or riskiest? Can such measures be accurately taken? And can you rely on information about airline safety on the internet?
A recent CNN.com story featured an interview with Carl Hoffman, a journalist who set out to travel on the world's most dangerous means of transportation, including some airlines. He chronicled his experiences in the book "The Lunatic Express."
Hoffman flew on two carriers that he respectively referred to as "statistically the most dangerous national airline in the world" and "the third most dangerous [carrier] in Latin America" in his book.
Hoffman used AirSafe.com as the source for his information, he said.
The website is run by Todd Curtis, a former Boeing airline safety engineer. It lists the "fatal event rate" per million flights for various airlines in North America, Latin America and the Caribbean, Europe, Africa and the Middle East, and Asia and Australasia.
To calculate the fatal event rates, Curtis said, he tracks any airline incidents that have involved at least one passenger death since 1970 and estimates that airline's number of flights in that period of time. He then uses a formula that takes into consideration the proportion of people killed per incident and divides that by the number of flights.
To collect the information, Curtis uses sources including the NTSB database, the databases of other major national safety organizations and publications like Flight International, an aerospace weekly founded in 1909 that covers aviation.
It's much easier to track the number of deaths than the number of each airline's total flights, he said, adding that he doesn't update the latter figure as often as the first. His website advises that because the number of flights for each airline is an estimate, the fatal event rate is also an estimate.
Curtis cautioned that people trying to gauge an airline's safety should not just compare carriers to each other based on the fatal event rates on his website, especially when it comes to airlines in different parts of the world. Other factors to consider include fleet size, crew training and the condition of the airports a carrier most often uses.
"If you have two airlines roughly the same size in the same country and the same number of flights over X number of years, one has one fatal event and the other has 15, well, there's red flags all over the place," Curtis said.
"But if one is in a developing country and they fly in a range of airports that are totally unlike what you see in the United States and you have a higher rate, it doesn't necessarily mean it's an unsafe airline. It just means the context in which this airline is flying has higher inherent risk than a comparison airline, let's say, in the United States."
Websites like AirSafe.com can provide a general snapshot of regional aviation safety, Feith said, but he cautioned against using them to compare individual airlines.
"I'm a safety guy, so when I look at stuff like that, I always want to see what forms the basis of those statistics and they don't have a lot of detail for me," Feith said.
So if you're using an unfamiliar airline, what can you do?
Travelers flying out of the country can check out the general aviation situation in other parts of the world via the FAA's International Aviation Safety Assessment program, which evaluates the ability of a nation's civil aviation authority to enforce its aviation system according to international standards.
"We classify the countries as either Category 1, which means they fully meet all the international standards, or Category 2, which means that they're deficient in some area. But again, that does not refer to individual airlines," Dorr said.
Current Category 2 countries on the list include Bangladesh, Croatia and Guyana.
Flying on a carrier that is a member of one of the global airline partnership programs ensures a higher level of safety, Feith said. U.S. carriers that team up with a foreign airline have to audit that partner to ensure that it's operating at a level of safety expected by the FAA, he added.
"The good rule of thumb is, always fly with a codeshare partner airline, whether it is in the Star Alliance program or the Oneworld or all of those other programs that exist, because the airlines have to audit each other," Feith said.
Also look for airlines that are members of the International Air Transport Association and are certified to fly internationally by the FAA and European regulators, McGee advised.