The U.S. Air Force is considering options to replace its aging fleet of supersonic T-38s.

No official tender or announcement has been made. But since its induction to the Air Force decades ago, scores of fighter and bomber pilots have trained on some version of the T-38 Talon, the world's first supersonic trainer jet.

"It takes years to procure a new trainer, so we need to start the process now," Gen. Stephen Lorenz, the outgoing commander of Air Education and Training Command was quoted saying by the Air Force Times. "The T-38 is getting old," Lorenz told officials at Randolph Air Force Base, in Texas.

Built by Northrop, the T-38 is a supersonic, a twin-engine, high-altitude aircraft used by the U.S. Naval Test Pilot School in predominance. NASA also uses the plane as a jet trainer for its astronauts, as well as a chase plane.

Two fatal crashes -- one at Columbus Air Force Base in Mississippi and the second at Sheppard Air Force Base in Wichita Falls, Texas -- resulted in four fatalities, leading the Air Force to temporarily ground the aircraft.

Air Force officials say an analysis of the trainers' replacement is being reviewed by the Air Force Training Command, with a decision expected by the end of the year.

"We're looking at performance, operational effectiveness, operational suitability, the cost to meet your capability needs, at advantages and disadvantages," the Air Force Times quoted Dave McDonald, a former trainer pilot, as saying. "Cost and capabilities are the big two, I would say."

McDonald is leading the review effort as program requirements manager for the advance trainer replacement program.

For years, a program caller Pacer Classic, opted to afford structural life extension for the T-38, integrating 10 modifications, including major structural renewal. The service life of most T-38s was extended to 2010.

The airplane, with swept-back wings, a streamlined fuselage and tricycle landing gear, has an exceptional safety record. But the Talons average about 44 years old and inspectors say they have increasingly been "showing their age."

"We need to build a new trainer that is economical, efficient and effective," Lorenz, the U.S. Navy training commander, said.

Upgrades carried out five years ago resulted in the T-38s sporting digital and glass cockpit displays, similar to those in newer jets. The planes are intended to fly 7,000 hours but they have already clocked more than double that.

"We're working hard on this," Lorenz said. "We're trying to follow due procedure so that someday soon the Air Force will be able to procure a new trainer … because this will be a 30-year decision when we buy this trainer."