The F-35B conducted its first flight out of Eglin AFB, Fla., May 22, marking one of several steps needed to officially stand up pilot training for the Lockheed Martin stealthy jet there.

The first F-35A conventional-takeoff-and-landing aircraft arrived at Eglin in July 2011 and the first B variant, optimized for the Marine Corps’ short-takeoff-and-vertical-landing requirement, arrived in January. Twelve F-35s are now at the base. Though pilot training was slated to start last fall, concerns raised by the Pentagon’s test community about the maturity of the aircraft and its software prompted the Air Force and Navy to delay this milestone.

The first F-35A “orientation” flight at Eglin took place in March. The goal is to start an operational utility evaluation (OUE) this summer using six F-35As.

The OUE will be managed by Air Force and Navy flight-testing experts, and the outcome of the exercise will determine whether Air Education and Training Command approves the initiation of formal pilot training. Though not a “go-to-war” configuration, the early training and OUE will use the Block 1A software, which allows for basic flight controls but lacks advanced capabilities such as weapons release.

The start of training is a key milestone for the F-35 program, which has suffered from production and testing delays. Trained pilots and maintainers are needed for the services to declare initial operational capability (IOC) with their F-35 versions. The Marine Corps will likely be the first, with a goal of IOC as soon as the next couple of years. Once F-35s begin entering the fleets, the services can begin retiring older fighters that are costly to maintain.

To date, 47 F-35A sorties have been executed at Eglin in addition to today’s F-35B flight, says Chrissy Cuttita, a spokeswoman for the base.

During the lull between deliveries and flights, the 33rd Fighter Wing used the aircraft for ground-based maintenance training.