Prepare for fierce aerial combat with aircraft that span the years since the dawn of aviation. Your time-ship's first encounter is with ancient 1910 biplanes; you're outnumbered, but your weapons are superior. Eliminate the entire air fleet; then knock out a mighty zeppelin and you'll progress to the next stage: 1940 monoplanes. These World War II fighters present a tougher challenge, and if you can defeat them, you'll move on to 1970 helicopters. Down the choppers and warp ahead to meet 1983 super jets. If you find a way to beat them, you'll cross the final barrier and head into the future for a deep-space duel with deadly flying saucers from the year 2001!