U.S. Army soldiers board a CH-47 Chinook helicopter at Allen Army Airfield, Fort Greeley, Alaska, on Feb. 23, 1998, during Exercise Northern Edge 98. More than 90,000 soldiers, sailors, Marines, airmen Coast Guardsmen and National Guardsmen are participating the exercise. Northern Edge 98 is designed to practice joint operational techniques and procedures, increasing interoperability between the services.