Grant from Bowen Island BC has a problem of air in his hot water line first thing in the morning and anytime after the system has been sitting still for a while. There are really only two sources of air to cause this problem.
Since Grant is on a well, it is possible that the check valves that prevent the water from going back towards the well, are not closing. Over a period of time, water falling back into the well could draw air into the line, probably from the pressure tank. Cleaning or repairing the check valves could solve the problem.
The other possibility is if the hot water tank is overheating (too high a temperature setting or full of sludge) causing air to boil out of the water whenever things are sitting still. This is more possible on a well system than in a city system because the overall water pressure is probably lower. Of course I didn't think about this second possibility until after Grant hung up. That's the advantage of the Web over TV -- I get to add in second thoughts.