Columbus Air Force Base in Mississippi grounded its T-38C training aircraft for a day after three contract maintainers were injured in an on-the-ground ejection seat accident Tuesday.

The T-38s resumed flying Wednesday morning, Staff Sgt. Joshua Smoot, a spokesman for the 14th Flying Training Wing at the base, said in an email.

Columbus said in a Tuesday release that the rear cockpit ejection seat of a T-38 inadvertently fired off at about 7:47 a.m., injuring three maintainers from Vertex Aerospace who were inspecting it. The maintainers were taken to a local hospital for treatment and released later that day.

The base is investigating the mishap.

A faulty ejection seat in a B-1B Lancer from Dyess Air Force Base in Texas also caused trouble in a separate incident in May. That bomber had a potentially catastrophic engine fire while in flight, and the four-airman crew blew the hatch to try to eject. But one of the four seats was unable to eject, so the crew stayed with the plane and was able to safely land at Midland International Air and Space Port in Texas.

The Air Force earlier this year ordered a one-day safety stand-down of all flying and maintenance wings after a series of troubling aircraft mishaps and crashes, several of which were fatal. The Air Force is also seeing an increase in lower-level Class C mishaps in recent years. But although Class C mishaps are not as serious as Class A and B mishaps — which sometimes can result in disabilities, deaths, or the loss of aircraft — experts say they can sometimes be a sign that more serious problems could be coming in the future.