A CRJ-200 jet manufactured by Bombardier of Montreal, the same makers of the CRJ-900 jet that was forced to land at JFK on Saturday night, was forced to make an emergency landing in Milwaukee yesterday when only two of its three sets of landing gear would lower. The landing was the sixth time in two years that planes from that company have been forced to land due to faulty landing gear. The CRJ-series jets were designed as commuter planes for short trips, often having to take off and land multiple times a day.