When flight investigators determine the cause of an airline accident, such as Continental's in Denver Saturday, they can work to prevent the same type of accident from happening again, the idea being to stop crashes before they happen.
But one key program designed to do just that is now on hold at a number of major airlines.
The Aviation Safety Action Program, spearheaded by the Federal Aviation Administration, has been critical, as it allows pilots and other airline workers to report their mistakes or safety problems without fear of punishment.
"I would go so far as to say that any airline that drops out of this program, people should not fly," ABC News aviation analyst John Nance said.
Four major airlines -- Delta, American, US Airways and Comair -- are, at least temporarily, no longer using the reporting program, raising alarm bells among aviation safety officials.
Delta suspended the program in 2006. The program lapsed at American in October 2008 and ended at US Airways last Saturday.
"These are programs that enable the carriers and all the stakeholders to understand and see trends early, before they become serious issues," Mark Rosenker, the acting chairman of the National Transportation Safety Board said.
At American Airlines, pilots reported about 5,800 safety incidents under the program last year.
Airline pilots can still report safety problems through a separate federal program called the Aviation Safety Reporting System, which NASA administers.
"American Airlines would dearly love to have ASAP back and in effect for our pilot's organization, and anytime the Airline Pilots Association is willing to come back, we stand ready to do it in a heartbeat," American Airlines spokesman Tim Wagner said.
Both management and pilots insist they support the safety program. The conflict comes because the two sides can't reach agreement on the protection pilots should have when they admit to a mistake.
"When a pilot reports a safety issue, we're seeing other discipline meted out," said Capt. John Prater, president of the Airline Pilot's Association. "We must stop that. Otherwise these programs will not move forward."
US Airways spokeswoman Morgan Durant said, "There are still other avenues for pilots to disclose any errors and not be subject to discipline. We have an internal program that we intend to keep going."
Airline companies insist they're only punishing pilots when it's appropriate.
"They've taken the trust this was based on and crumpled it up and thrown it in the wastebasket. All we want is to put the discipline genie back in its box," said American Airlines Capt. Tom Westbrook.
Either way, a key safety program is on the ropes. "This is really very, I'll just use the word, a stupid thing to do. It's an idiotic thing to do. It's unacceptable and has to be reversed, period," said Nance.
"Using safety as a chip at the bargaining table is unconscionable," said acting FAA administrator Robert A. Sturgell. "It's in everyone's best interest to separate safety from labor issues. These voluntary reporting programs are crucial to safety, and it's disappointing to see them cast aside at a time when they're needed most."
This story was originally published Dec. 21, 2008, and updated Dec. 22, 2008.