The U.S. Navy announced Wednesday it has grounded all T-45 Goshawk jet training flights for three days, after Fox News reported that up to 100 instructor pilots were refusing to fly the aircraft citing problems with its oxygen system.

“We take the concerns of our aircrew seriously and have directed a ... safety pause for the T-45 community to allow time for Naval Aviation leadership to engage with the pilots, hear their concerns and discuss the risk mitigations as well as the efforts that are ongoing to correct this issue,” Navy spokeswoman Cmdr. Jeannie Groeneveld said in an email to Fox News Wednesday.

As Fox News reported Tuesday, the boycott started late last week and had effectively grounded hundreds of training flights already.

The head of U.S. Navy flight training, Rear Adm. Dell Bull, was supposed to visit pilots at Naval Air Station in Meridian, Miss., Wednesday, but cancelled that visit abruptly to brief senior Naval officers on a video teleconference from Pensacola, multiple Navy officials told Fox News.

Naval aviation leaders are planning to visit all three bases where T-45s are flown to meet with the pilots and hear their concerns.

“The pilots don’t feel safe flying this aircraft,” one instructor pilot told Fox News.

Among the hundreds of student pilots affected is Marine 1st Lt. Michael Pence, son of Vice President Pence – a factor that could put added pressure on the Pentagon to resolve the dispute.

Vice Adm. Mike Shoemaker, head of naval aviation, told Fox News in an exclusive interview that the training jet issue is the “number one safety priority” across naval aviation right now.

In the last five years, physiological episodes, caused in part by problems with the oxygen system, have nearly quadrupled on the T-45 training jet, according to Capitol Hill testimony last week by senior naval aviators.

Sen. John McCain, R-Ariz., said in a statement that the Navy “must address these safety concerns swiftly and decisively.”

“I am disappointed the situation has devolved to the point some instructor pilots, who feel strongly that their concerns are not being addressed, have removed themselves from what they love most--flying Navy aircraft,” McCain added.

Fox News interviewed multiple Navy flight instructors who say incidents of oxygen poisoning in the 30-year old T-45 Goshawk have “skyrocketed.”

“Histotoxic hypoxia” is the medical term associated with the disorientating disorder which can put pilots’ lives at risk, as well as those of civilians on the ground below. Two instructor pilots say the training jets are now averaging three incidents a week, as the Navy struggles to get to the bottom of the contamination.

“It can happen without warning,” one pilot said. “The system doesn’t detect contaminants.”

A number of instructors cited recent episodes as reasons for the abrupt work stoppage.

Last week, a student from training squadron VT-86 in Pensacola, Fla., had to be “dragged out” of his jet because he became “incapacitated” from the faulty oxygen system, according to two flight instructors.

In March, a British exchange instructor pilot with thousands of hours in the cockpit had to conduct an emergency landing during a training flight near Meridian, Miss., after both he and his student experienced hypoxic symptoms.

In August, a flight instructor and his student were forced to eject near Kingsville, Texas, when they felt symptoms of hypoxia, crashing the multi-million dollar jet. Both pilots ejected safely and were not seriously injured.

Last month, there were 10 episodes in T-45s, according to Shoemaker.

Anticipating the pilot protest, the Navy sent a team of engineers and other specialists this week to its T-45 training bases in Kingsville, Meridian and Pensacola for talks with the pilots.

A meeting Tuesday in Meridian “got heated,” Fox News is told. The pilots told the civilians from Navy Air Systems Command their complaints about the oxygen system were being ignored. When a senior Navy pilot showed photos of a faulty oxygen system he claimed had been sent up to NAVAIR’s headquarters in Maryland, the engineers said they never received the photos.