While landing at Downsview, the aircraft landed with the undercarriage retracted. The experimental Global Express aircraft, prototype no,3, was on the fourth flight of the day. The aircraft came to rest on the runway with the landing gear retracted. For the purposes of the tests to be performed during the flight, the GPWS was rendered inoperable before the flight began. During the flight, the crew disarmed the audible warning system to conduct tests. The audible warning system was never re-armed. Under normal circumstances, with the GPWS functioning and despite the audible warning system being disarmed, the flight crew would have received a “too low-gear” warning from the GPWS beginning when the aircraft descended below 900 feet agl. The landing gear was never selected “down” according to the CVR (the captain did not request that the gear be lowered prior to landing). The flight crew reported that they were not following the checklist prior to landing. The gear did not collapse as reported initially.