Delta 2311’s 27,000-Foot Drop Followed the Oxygen Rules

Delta Flight 2311 dropped about 27,000 feet in 10 minutes on Sept. 6 after a cabin pressure failure, then landed in Las Vegas. The Boeing 737-900ER was flying from Los Angeles to Salt Lake City with 174 passengers and six crew when the masks fell.

Federal oxygen rules already size crew bottles around a 10-minute trip down to 10,000 feet. The pilots asked for 9,000 feet and a straight line to Harry Reid International Airport.

Delta 2311 Told Controllers It Was Already Coming Down

Flight-tracking records put the jet, registration N934DZ, at about 36,200 feet when the crew started down. They did not read a mayday on the clip that circulated after the flight. They named the maneuver and the airport they wanted.

Delta 2311 currently rapid descent. We’d like to get down to 9,000, and we’re direct to Las Vegas.

Delta 2311 crew, air traffic control radio

A controller asked if oxygen had deployed. The pilot said, “Affirmative.” Controllers cleared the 737 to 9,000 feet, pointed it at Harry Reid, and told the crew to expect Runway 26L.

Matthew “Whiz” Buckley, a retired U.S. Navy F/A-18 pilot with nearly 40 years of flying, said a pressurization failure of this kind is extremely rare in the United States. He said crews in that spot are trained to land as soon as practical at the closest field with a runway that can take the airplane, which is why Las Vegas beat Salt Lake City.

The FAA later said the Boeing 737 diverted safely to Harry Reid International around 6 p.m. local time after the crew reported a pressurization issue. Flight-tracking stamps put the landing at 6:16 p.m. Pacific, the same arrival. Passengers walked off normally. Delta put them on another airplane to Salt Lake City. No injuries were reported.

The 10-Minute Drop Is Written Into Federal Rules

Headlines treated 27,000 feet in 10 minutes as a fall. That window is also how U.S. airline oxygen rules are built. Under descent to 10,000 feet in ten minutes, a carrier has to carry enough crew oxygen for a constant-rate drop from the jet’s maximum operating altitude to 10,000 feet, then 110 minutes more at 10,000 feet.

Passenger systems have a shorter job. For jets cruising above flight level 250, the same rule requires not less than a 10-minute oxygen supply in the cabin after a pressure loss, enough to cover the trip into thicker air. Chemical generators behind those yellow masks are built around that clock, not around a sightseeing descent.

On a normal cruise the cabin is held far below the airplane. Certification rules require a cabin altitude of 8,000 feet or lower in ordinary flight. Masks drop when cabin altitude climbs through about 14,000 feet, a trip point on the pressure system, not a reading of how high the jet is over the desert. If those bags fell on Delta 2311, the cabin had already left the band people can sit in without extra oxygen.

THE DESCENT ON THE CLOCK

Training films of a 737 emergency descent often show idle thrust, speedbrakes, and a dive well above 5,000 feet a minute. The published 10-minute profile on this flight averages about 2,700 feet a minute. That is still a rapid descent. It is also the same 10-minute box the oxygen rule already assumes, not a jet with no one at the controls.

What the 737 Checklist Tells the Crew to Do

Boeing 737 crews do not invent this sequence on the radio. Johan Percherin, a 737 type-rated airline pilot, lays out the 737 cabin altitude warning memory items as actions that have to be known by heart before anyone opens the handbook.

The first moves are oxygen and talk. Masks go on, regulators go to 100 percent, and the two pilots confirm they can still hear each other, because hypoxia can take useful thought in under a minute at high cabin altitude. Then the pressurization panel goes to manual and the outflow valve is driven closed. If cabin altitude keeps climbing, passenger signs and passenger oxygen go on and the crew runs the emergency descent.

737 MEMORY ITEMS

• Oxygen first: Don masks, set 100 percent, and establish crew communications before anyone troubleshoots the panel.
• Try to hold the cabin: Switch pressurization to manual and hold the outflow valve closed until it shows fully shut.
• If it will not hold: Passenger signs on, passenger oxygen on, then the emergency descent checklist.
• The dive: Descend without delay to 10,000 feet or the lowest safe altitude, whichever is higher, with thrust at minimum and speedbrakes at flight detent.
• The PA: The pilot flying calls “emergency descent” three times so the cabin knows a rapid drop is coming.

That last item is the one that failed the people in the back. Full-face crew masks have microphones, which is why the radio call to Las Vegas is clear. Cabin attendant masks do not. A crew that is doing the procedure correctly can still sound like silence in row 22.

Masks On, the Cabin PA Went Dead

One passenger who wrote after the flight said ears hurt at once, the masks dropped, and the airplane started down toward Las Vegas. The dive was not the worst part of it.

The scariest part wasn’t even the descent: it was not knowing what was going on. Flight attendants were trying to make announcements with their masks on and it was almost impossible to hear them. The cabin was confused and pretty panicked.

Passenger on Delta 2311, written after the flight

That is a communications failure riding on top of a procedure that worked. The pilots could talk to Las Vegas. The cabin could not hear a usable explanation through mask fabric and engine noise while the 737 lost tens of thousands of feet. People reached for yellow plastic and waited, which is what the safety card asks them to do, and the wait felt like a mystery because the PA could not carry a sentence.

Delta later said the crew followed training and procedures to bring the aircraft to an optimal altitude after an unexpected pressurization issue. A spokesperson also said the airline “sincerely apologizes to our customers for their experience and thanks our flight crews and other support teams on the ground for their professionalism.”

N934DZ Sat in Las Vegas Until Sept. 9

N934DZ is a 2012 Boeing 737-9GP(ER), constructor number 37289, the type sold as a 737-900ER. Delta Air Lines took it onto the U.S. registry on Feb. 16, 2023, after time with Lion Air. By Sept. 6 it was a 14-year-old domestic workhorse, not a new jet, and it had already flown Las Vegas-Los Angeles legs that same day before it launched as Flight 2311.

Some early roundups treated the airframe as if it had been patched and sent on to Salt Lake City that night. The passengers did go on, on a different airplane. N934DZ Boeing 737-900ER flight history shows the jet remaining in Las Vegas until the morning of Sept. 9, when it left as DL9962 to Detroit, about 64 hours after the 6:16 p.m. landing.

FROM LAX TO DETROIT, WITH A STOP THAT WAS NOT ON THE TICKET

1. Sept. 6, 2026, 4:54 p.m. PDT: Flight-tracking records show N934DZ taking off from Los Angeles as Delta 2311, scheduled for Salt Lake City.
2. Sept. 6, during cruise: At about 36,200 feet the crew reports a pressurization problem, passenger masks deploy, and the 737 starts a rapid descent toward 9,000 feet, direct Las Vegas.
3. Sept. 6, 6:16 p.m. PDT: The jet lands at Harry Reid International Airport on the Runway 26L routing controllers had issued. Passengers deplane normally and Delta arranges another aircraft to Salt Lake City.
4. Sept. 9, 10:22 a.m. PDT: N934DZ leaves Las Vegas for Detroit as DL9962, a 3-hour 18-minute hop that puts the airframe back into scheduled service after the ground hold.

A pressure fault that can be cleared in a couple of hours is often a controller or a valve. A three-day sit is a longer look. Delta has not said which unit failed, and the FAA has not published a cause.

Four Days Later a Delta 757 Turned Back at JFK

Flight 2311 was not the only Delta pressure call in the FAA’s incident log this late summer. On Aug. 9, Delta Flight 2122 landed in Denver at about 7:15 p.m. after the crew reported a pressurization issue. On Sept. 10, four days after the Las Vegas diversion, Delta Flight 791, a Boeing 757 headed from New York to Phoenix, returned to Kennedy at about 10:25 a.m. after a possible pressurization issue. The FAA said it will investigate those flights too.

DELTA PRESSURIZATION CALLS IN THE FAA LOG

Three logged pressure events do not prove a common part. They do mean Flight 2311 is sitting in a short run of Delta reports, not in a vacuum, and that the agency is treating each one as its own file. Public reporting has not tied N934DZ to a fleet-wide inspection order or a grounding.

WHAT WE KNOW

• The flight: Delta 2311, Los Angeles to Salt Lake City on Sept. 6, 2026, 174 passengers and six crew on a 737-900ER.
• The maneuver: About 27,000 feet down in about 10 minutes, masks out, radio call for 9,000 feet and Las Vegas, landing on the 26L routing.
• The people: No injuries reported; passengers left the airplane normally and continued on a replacement jet.
• The airframe: N934DZ stayed in Las Vegas until Sept. 9, then flew to Detroit as DL9962.

WHAT IS UNCONFIRMED

• The failed part: Valve, sensor, controller, seal, or software has not been named.
• How fast the cabin climbed: No public readout of cabin altitude or differential pressure has been released.
• Whether DL791 or DL2122 share a cause: The FAA has opened files; it has not linked the three.

N934DZ is flying again. The FAA still has not said what failed in the pressure system on Flight 2311. Until it does, the public record is a calm radio call, a 10-minute descent, and a landing on Runway 26L.