The Navy training jet that crashed Sunday in Monroe County, killing two on board, had a recently installed monitor to help the pilots check oxygen pressure, a concern earlier this year by many in the military who fly the aircraft.

Responding to queries from 10News, Lt. Elizabeth Feaster said the T-45 that went down in the Cherokee National Forest featured what's called the CRU-123 oxygen monitoring system.

In March, Navy pilots demanded the department look into a rising number of "physiological episodes," incidents in which aircrew performance suffered because of contaminated air, changes in the cabin pressure or other problems inside the plane.

Dozens of trainer jets were grounded briefly this year, flights were kept to low altitudes and the Navy ordered a comprehensive review of the T-45 and the F/18.

Photo: Aircraft manufacturer Boeing

Jets resumed flying after several months.

The jets are based at naval bases in Pensacola, Fla., Kingsville, Texas, and Meridian, Miss., which was the origin of the flight that crashed Sunday, killing two pilots in the forest in Monroe County.

Last summer's review cited concerns about on-board oxygen systems and included recommendations that the Navy give pilots greater assurance the air they were breathing was safe.

As a result, the Navy is installing the CRU-123 monitoring systems.

Teaster told 10News that as of Oct. 1 "113 of 170 T-45s have been outfitted with CRU-123 oxygen monitor systems, another measure to 'Inform the Aircrew' to provide additional indications in the cockpit.

"We assess that all T-45 aircraft will have the CRU-123 installed by the end of the second quarter of 2018."

Navy crews are at the national forest investigating the crash that killed Lt. Patrick L. Ruth, of Metairie, La., and Lt. j.g. Wallace E. Burch, of Horn Lake, Miss. They don't know what led to the crash.

The investigation may take months.

Teaster said the Navy can't know right now whether the aircraft's on-board oxygen system played a role in what happened, "but we are looking at all possible causes for the mishap."

Meridian-based Training Wing One resumed T-45 training flights Aug. 1, according to Teaster.

The aircraft are used to train pilots how to fly on and off aircraft carriers.

Related: Oxygen problems prompt Navy review of T-45

On Thursday, the U.S. Forest Service reminded East Tennesseans it has closed part of the Tellico Ranger District in the Cherokee National Forest to the public as the investigation into plane crash continues.

The closure will be temporary until the investigation is finished and includes the following areas:

  • FS-RD 210 - Tellico River Road from Pheasant Field Picnic Area to Stateline Campground
  • FS-RD - Beaverdam Bald Road
  • FS-RD 61 - Whigg Meadow Road
  • FS-RD – 40841
  • FS-RD – 40921
  • FS-RD – 2417 – Big Cove Branch Road
  • Benton MacKaye Trail #2 from Sandy Gap to Mud Gap
  • Kirkland Creek Trail (#85)
  • Whigg Ridge Trail (#86)
  • Brookshire Creek Trail (#180)

Both pilots were assigned to the "Eagles" of Training Squadron (VT) 7 based at Naval Air Station Meridian.

Ruth had been a member of the squadron since 2015, and had served in the Navy for nine years. Burch joined VT-7 in 2016, and had served in the Navy for three years.

The Navy previously said the T-45C Goshawk was carrying an instructor and a pilot when it crashed near Tellico Plains.