Press ~ to display the console, then type "map [level code]" using the following information to skip to the corresponding level:
 
Name Level code
Outer Base base1.bsp
Installation base2.bsp
Comm Center base3.bsp
Lost Station train.bsp
Ammo Depot bunk1.bsp
Supply Station ware1.bsp
Warehouse ware2.bsp
Main Gate jail1.bsp
Destination Center jail2.bsp
Security Complex jail3.bsp
Torture Chambers jail4.bsp
Guard House jail5.asp
Grid Control security.bsp
Mine Entrance mintro.asp
Upper Mines mine1.bsp
Borehole mine2.bsp
Drilling Area mine3.bsp
Lower Mines mine4.bsp
Receiving Center fact1.bsp
Sudden Death fact3.bsp
Processing Plant fact2.bsp
Power Plant power1.bsp
The Reactor power2.bsp
Cooling Facility cool1.bsp
Toxic Waste Dump waste1.bsp
Pumping Station 1 waste2.bsp
Pumping Station 2 waste3.bsp
Big Gun biggun.bsp
Outer Hangar hangar1.bsp
Comm Satelite space.bsp
Research Lab lab.bsp
Inner Hangar hangar2.bsp
Launch Command command.bsp
Outlands strike.bsp
Outer Courts city1.bsp
Lower Palace city2.bsp
Upper Palace city3.bsp
Inner Chamber boss1.bsp
Final Showdown boss2.bsp