Four U.S. Marines are presumed dead following yet another tragic incident involving Marine Corps aircraft on Tuesday. That crash was one of two incidents involving Marine Corps aircraft going down within just hours of each other.

The Marines were traveling over Southern California near the Mexican border when their CH-53 Super Stallion was lost on radar at approximately 2:35 p.m. local time. Thus far, very little information regarding the incident has been released by Marine Corps officials, though it is unusual for the branch to seem uncertain of the Marines fate even hours after the incident.

“The status of all four is presumed dead pending positive identification,” read a statement from the unit.

Once the status of the Marines have been confirmed, family notification procedures will be initiated and their identities will remain withheld for 24 hours as notification teams engage with the family.

An investigation is underway to determine the cause of the incident, but it seems likely that the crash may have been related to maintenance issues associated with inconsistent funding caused by lawmakers failing to pass defense budgets on a nearly annual basis.

According to a recent internal study conducted by the Marine Corps, budgeting issues have combined with the advancing age of America’s Super Stallion fleet to create an extremely dangerous situation. Overall, CH-53 Super Stallion readiness is rated at just 23 percent fleet wide. Of the 196 Super Stallions that are required to be operational at any given time, only 33 of them are actually considered combat capable, and the force has only 146 that could be repaired or serviced to bring back to operational standing.

The issue of having too few flight-capable CH-53s has also made it nearly impossible for pilots to receive adequate training on the air frame, increasing the likelihood of pilot error resulting in a crash.

“Pilots returning from six-month deployments with only 30 total flight hours and pilots completing their first operational tours with too few hours to become aircraft commanders,” The report read.