How do I fix air bubbles in my pool's return jets?

Start with the pump lid O-ring. Turn off the pump, remove the lid, wipe the O-ring and groove clean, then apply a thin layer of silicone lubricant. Re-seat the lid and tighten by hand. If that doesn’t fix it, check the skimmer weir door and the pump housing drain plug. Most people stop at the O-ring and fix it.