The commandant of the Marine Corps said the service can not meet training requirements under current budgets when questioned by lawmakers on Wednesday about the steep increase in major aircraft accidents.

Rep. Mac Thornberry, R-Texas, and chairman of the House Armed Services Committee, asked Gen. Robert Neller about why the number of serious air accidents has "been increasing significantly" over the past three years.

"We track this very closely and the simple fact is we don't have enough airplanes to meet training requirements for the entire force," Neller told lawmakers at a hearing of the House Armed Services Committee on the fiscal 2017 budget request.

He stressed that Marines who deploy are "trained and ready," but that non-deployed forces' training may not be good enough.

Neller was referring to Class A aviation mishaps, defined as one that damages $1 million or more in property, destroys a military aircraft or kills or permanently disables a person, according to the Marine Corps. Thornberry said that in 2015, the service suffered 2.57 Class A mishaps per 100,000 flying hours. By 2016, that number had increased to 3.96 per 100,000 hours.

On Jan. 14, two CH-53E Sea Stallion helicopters collided during nighttime training off Hawaii, killing all 12 Marines aboard.

Training has taken a hit in recent budget cycles as military officials work to fund today's wars at the expense of future readiness under tight budgets. Officials have told lawmakers that they were mortgaging the military's future to ensure troops who deploy today are as safe and prepared as possible.

"The real bill payer for underfunded readiness is lost lives. I think that helps bring it into context for all of us," Thornberry said in his opening statement.

Thornberry said the Army has also seen an increase in mishaps from 1.52 per 100,000 flying hours in fiscal 2014 to almost 2 in fiscal 2016.

Gen. Mark Milley, the Army chief of staff, said the Army has commissioned a "very detailed study" on why accidents are on the rise. He said he expected to have more data in about a month.

Milley also said that the fiscal 2017 budget increases monthly flying hours for helicopter pilots from 10 to 12.

"We want 14, 15 hours per month, but we can't get there with this budget," he said.