Otherwise you could try using the glitching through walls glitch to get into them. I couldn't manage to get into the Oahu airport as it seems the glitch doesn't work on the fence surrounding it and at the walls you get the promt to press A to enter the airport and trying the glitch there dumps you back at the nearest road. I did manage to get into the airport far south of Oahu though. I did the going through walls glitch on a building there and got through.
EDIT: Forgot to mention the south Oahu airport doesn't have proper tracks. It's all low res and your car drives on it as though it's offroad.
"It's you Americans. There's something about nipples you hate. If this were Germany, we'd be romping around naked on the stage here." - Peter Molyneux