Keeping textures in memory

I'm working on scenery for CYCD, Nanaimo airport in BC. I've noticed that when I pan arround my airport, the textures dont seem to stay in memory, but are constantly being reloaded from the hard drive, which causes the sim to stutter and pause. I've seen other sceneries that don't do this. I'm building the airport using FSDS 2.4 and FSSC 1.511 (I think). All of my textures are 512 x 512, 8 bit color. Does anyone know if it's possible to do something to tell the sim to keep the textures in memory?ThanksPS. A preview of the scenery can be found here, if anyone is interested:http://www.vanisleva.com/forum/viewtopic.php?t=34