Air Force Chief of Staff Gen. Mark Welsh today defended the F-35 Joint Strike Fighter program's work on software, widely considered the biggest risk in the aircraft's development, but did not rule out the prospect of more delays. Asked whether software problems could further slow the program's schedule, Welsh told reporters at the Pentagon, “I don't know what we're going to see.” But he said he and program officials are “confident” they will “get the software versions in place” required...