More than half of U.S. commercial airports don't have a 1,000-foot margin at the end of a runway, an overrun area the federal government says is needed as a safety zone, according to a new report.

Some of the busiest airports in the country — including Los Angeles International Airport, Chicago's O'Hare International Airport and Hartsfield-Jackson Atlanta International Airport — have more than one runway that doesn't meet safety standards, according to statistics supplied by the Federal Aviation Administration.

"Our runways are out of shape, and the Bush administration has failed to move to correct the problem," Sen. Frank Lautenberg, a New Jersey Democrat, said Thursday. "If we don't get serious about runway problems, the result could be disastrous."

The FAA says it is diligently upgrading the runways. The agency expects that all of them will meet the standard by 2015, when they are legally required to do so, according to FAA spokeswoman Laura Brown.

"Today, 70 percent of commercial service runways have a runway safety area within 90 percent of the standard," Brown said. She said 236 runways were improved as of Sept. 22.

At 325 airports — more than half of the 573 commercial airports in the United States — at least one runway lacks the 1,000-foot safety zone, according to the FAA's own figures. Almost half of all commercial runways — 507 of 1,017 — don't meet the safety standard.

Deadly airplane crashes can happen on runways because they're too short, improperly lit, poorly designed or lack safety equipment. A minor procedural error by a pilot or an air traffic controller can turn tragic if a vehicle or another airplane happens to be in the way.

Federal safety investigators are looking into three runway mishaps this week alone: An Alaska Airlines jet took off on the wrong runway at Seattle-Tacoma International Airport; two airliners clipped wings while taxiing at Newark Liberty International Airport; and another jet landed on a taxiway at Newark.

The wrong runway may have been used more frequently than the FAA previously thought. The agency searched 5.4 million records over 10 years and found flight crews said they were confused about runways 117 times, according to FAA spokeswoman Laura Brown.

As a result of the data search, Brown said, the FAA is exploring ways to prevent pilot confusion.

Within the past year, two fatal commercial airline crashes involved runways.

In August, 49 people were killed when a Comair regional jet took off on the wrong runway at Lexington Blue Grass Airport in Kentucky.

In December, a 6-year-old boy in a car was killed when a Southwest Airlines 737 overran a runway at Chicago's Midway Airport and plowed into the street.

There have been 45 fatal crashes due to aircraft overrunning runways since 1983, according to Lautenberg.

Part of the problem is that some airports were built in congested urban areas and have no room to lengthen their runways.

One solution is to install soft concrete beds at the end of a runway. Called Engineered Material Arresting Systems, or EMAS, they slow an airplane that rolls off the end of a runway.

Last month, a private jet carrying Yankees third baseman Alex Rodriguez overran a runway at Bob Hope Airport in Burbank, Calif., and was brought to a halt by an EMAS bed.