For an infinite current sheet whose current has always been on, it is well known that a purely magnetic field exists on each side, in all of space. For an infinite current sheet whose current is initially off, then suddenly turned on everywhere simultaneously, I think I have worked out that a "front" of electromagnetic fields propagates from the sheet at c. Outside the front, there are no fields, of course. Inside the front, there are crossed electric and magnetic fields, both of which are time- and space-invariant. This result surprised me initially. I thought there would only be a magnetic field inside the front. But EM radiation is constantly arriving from more and more distant radii of the current sheet, contributing to a constant electric field. Does this sound correct?