It is held by two bolts in the front of the tank. However, you may have to take inner fairing pieces that are near the front of the tank and your seat to make it easy on you. Once you take those two bolts off, just lifted up and hold it up with a bungee cord that is hooked up to the back of your bike or have somebody hold it for you. You don't have to take the tank totally off to get to the air box. You might want to do this when tank is not full, otherwise you will have gas spill out of your overflow hose.
Also be careful with the hoses and tank sensor wires under the tank when you are lifting it up.
Not sure on an 04 but on my 09 you just remove the two bolts at the front and the tank just lifts up, it is hinged at the back. I just used some bungees hooked to an awning to hold the tank up and changed the air filter. Just be sure no hoses are pinched when you put it all back together.