Federal authorities are prohibiting all operators of McDonnell Douglas MD-11 planes from flying the aircraft until they are inspected after a UPS cargo plane crashed into a ball of flames shortly after taking off from Louisville Muhammad Ali International Airport in Kentucky earlier this week.
The emergency directive from the Federal Aviation Administration on Saturday was "prompted by an accident where the left-hand engine and pylon detached from the airplane during takeoff," FAA documents said. "The cause of the detachment is currently under investigation. The unsafe condition could result in loss of continued safe flight and landing."
The directive prohibits flight until the aircraft are inspected and any fixes are made.
Earlier, the plane's maker, Boeing, recommended that the three operators of MD-11 aircrafts ground the planes.
"This recommendation was made in an abundance of caution and we will continue coordinating with the FAA on this matter," Boeing said in a statement.
There are about 70 MD-11s in service operated by UPS, FedEx and Western Global, according to Boeing.
Late Friday night, UPS said it was temporarily grounding its fleet of MD-11 aircraft, which make up about 9% of its fleet "out of an abundance of caution and in the interest of safety."
FedEx also confirmed it was immediately grounding its 28 MD-11 planes as it conducts a safety review.
Western Global has not yet responded to ABC News' request for comment.
The cause of the Louisville crash is still under investigation.
On Friday, the National Transportation Safety Board revealed more information about the crash, detailing the final moments in the cockpit of the UPS plane based on a review of the audio from the cockpit voice recorder.
The plane crew tried to control the aircraft for about 25 seconds before it crashed, an NTSB official said, citing preliminary information.
The official, Todd Inman, said the crew had completed their standard checklist and briefing and the takeoff roll was uneventful.
"About 37 seconds after the crew called for takeoff thrust, a repeating bell was heard" on the cockpit voice recorder, Inman said during a press briefing on Friday.
The bell "persisted until the end of recording 25 seconds later," when the plane is believed to have crashed, he said.
"During this time the crew engaged in efforts to attempt to control the aircraft before the crash," he said.
Inman said the bell may have indicated that there was a fire, as was evident from footage of the incident, but added that he didn't want to speculate too far.
"The FDR [flight data recorder] data and the examination by the groups on that will give us a lot more granularity and be able to help paint a better picture," he said.
The NTSB will work to produce a written transcript of the cockpit voice recorder audio, which will be made public likely several months from now, he said.
UPS Flight 2976 crashed around 5:15 p.m. local time on Tuesday, officials said. The plane was headed to Daniel K. Inouye International Airport in Honolulu when the plane's left engine detached after a "large plume of fire" erupted from the plane's left wing, according to the NTSB.
Inman said the bulk of the left engine pylon was still attached to the left engine when the engine separated from the wing. Both components are in a secure facility undergoing further examination.
The NTSB found additional pieces of the engine attachment in the grass near the runway, he said.
As crews continued to search through a half-mile of charred debris, a victim was located at the crash site on Friday, according to Louisville Mayor Craig Greenberg. That brings the confirmed death toll from the incident to 14, with the three pilots on board believed to be among those killed.
"We pray for each of the victims' families, and pray that no additional victims are lost as our first responders continue to search and seek answers that we all are looking for," he said in a video statement.
Editor's Note: This story has been updated to correct the name of the NSTB official who briefed reporters on the investigation into the crash.